user191: We (me and a vague but definitely real group of users) in the Maid Café would like to make some games. If you are interested, ping me in chat or post/comment here.
There are no limitations, but consider these things:

It should be fun. Pretty sure nobody here likes text-based "Choose your own adventure" genre, Match-3 or Pinball. Ask yourself if you would have fun making and then playing something;
If we want to make a game sooner rather than later, the core game should be short and simple to make;
If we want to make a game at all, 2D is the faster route than 3D.

Use answers for game propositions. If you have some other ideas, let's discuss them in chat.

Whatever you have in mind, don't hesitate to post it!
I'm just explaining my personal concerns about starting a collaborative project which often die soon because the goals are too high for project members. Compare the amount of artwork and story writing needed for an average VN and an average arcade game, and you'll see what I mean. But if suddenly a very dedicated group of people appears that want and will make a VN, I'd only be happy for them.
Part of the gig is learning how to use C#, Unity and whatnot for game development.

user19221: Trajectory shooting game
example: DDtank
Introduction
It might be difficult but its my suggestion because I love these types of games. Trajectory shooting game will be like every person will have their own weapon and that player will use that weapon to throw it in the air and kill his opponent by correct amount of strength. Since it will be trajectory motion therefore player can adjust their angle and then throw object to hit their target. Also this game might be calculative one because users have to first calculate the correct amount of power and angle to throw object so that it will hit the target.
Basic game:

Human vs Computer. Like both players having health and both of them trying to kill each other by throwing objects.
And Human vs Human matches.
Wind system like due to wind the trajectory motion gets disturbed which will make every round different and difficult.
There can be tutorial at starting showing how to play the game and how to improve their skills. It is important for players to learn how to play this game and how to calculate so that they can hit target.

Extended Game

We can use team vs team game match where every team got one chance to attack.
It can be boss level fight. Boss level fight means player have to complete each level to earn level or any item etc.
There can be armory settings like to increase defense and many more.
Restricting the angle for different weapons.
There can be different maps for various matches.


user1587: Murder Game - FPS
this idea was inspired by one Dark Brotherhood quest in The Elder Scrolls IV: Oblivion. all players are inside a single house and one of them is the murderer who has to pick off the remaining players without being caught.
the murderer is chosen at random and only the murderer will know at first. the other plays win if the catch the murderer. the Murderer will then have # minutes to commit their first kill before the game restarts and a new murder is select
in order to catch the murderer the suspect has to be detained by tying them up and placed in a zone for a certain amount of time until the suspect is taken out of the game. 
once the suspect has been removed from the game all players will see what the suspect saw during the time of each murder as such it will be clear what involvement, if any, the suspect had with any murders. the suspect can be freed before they are removed from the game either by other player or themselves (by having a crafted tool to help their own escape)
the game will be in the First Person so that players can see someone approaching from behind unless in front of a mirror and hopefully sound will be close to how it works in real life so that when players "sleep" they see a black screen (or some other animation as if dreaming) but they can still hear (so they can wake up if they hear a strange noise like someone sneaking about)
Basic Game

Single Map (Mansion Interiour)
Multi-Player Only
Needs (Like Hunger, Sleep, Toilet etc, like in The Sims)


this allows the murderer to drug/poison their victims food or try and kill during their sleep
if someone is expect to go take a bath the murderer can rig something up to kill them (ie. plugged in toast falls in)

Possible list of everyday tasks that players have to do one item on the list every # minutes


this prevents players just staying in one room
this forces the murderer to blend in aswell


Extended Game

Other Maps


Estate (includes Interiors and Exterior)
Hotel
Neighborhood (remember the Pint Size Slasher from Fallout 3?)

Other game modes


Hitman - the target is marked and everyone chooses roles. one player is randomly chosen as the Hitman to kill the target.
Death Note (Yes, a use for all those dam Death Note Puzzle Questions) - using the rules of the Death Note Kira goes to try and kill the players while they must find out who is Kira. may have to tweak the Death Note to prevent mass suicides and add a cool down time



user191: 2D Tower Defense
Like Orcs Must Die or Dungeon Defenders.
Basic game:

On a pre-made level enemies follow a path to the "End". If just one enemy reaches the end, you lose.
Enemies are generated in small batches. Let's say 1 every second for a batch of 5, with a delay of 20 seconds between batches.
Enemies can be killed by traps that automatically trigger when enemies step on them, and need 10 seconds to reset. Trap can kill all enemies within its trigger zone.
Player can install a limited number of traps throughout the level. Inefficient placement will result in enemies passing through them.
Player can kill all enemies within some range from the cursor, with a significant delay. We'll figure out the game balance in the process.

Extended game:

More levels with multiple paths, possibly randomly generated from pre-made chunks;
Enemy types resistant to certain attack types (like ice and fire);
Trap types more efficient and useless against various enemy types;
Different player attacks;
Better art and sound? eh 

If you're interested in this idea, or you want to propose changes, comment below.

user1587: TCG (Trading Card Game)
examples: Yu-Gi-Oh, Weiß Schwarz, Tanto Cuore
Basic Game:

1 VS 1 with a Computer Opponent
1 VS 1 with Human Opponent
1st Series of cards
In-game slideshow explaining rules

Extended Game

2 VS 2 Tag Team
More Series of cards
Playable Tutorial
Single Player Story Mode(s)


Unlocking of more AI Opponents with themed decks/strategies
A new Story Mode for every released series
Tutorial can be integrated into story


Notes

Card Game rules will need to be discussed (personally i liked Yu-Gi-Oh's approach)
New cards can be added later by players in a similar way to how League of Legends for Forum RPGs allows players to make new Characters


user1587: This was an idea for a game i thought up while playing Minecraft and tried to duplicate with mods but couldn't get close. the idea is that you would find a town and set yourself up with a job there whether that be starting a farm to supply their food or working, a guard to protect it or a smith/builder.
with these jobs you have different levels of responsibility ie.

with the farmer you with just harvest the crops or own the farm itself and handle all the fiances including hiring other farm hands
with a guard you can just follow your orders or be the town commander and order where your guards patrol

and later if you don't want to be tied down in a single town you can go out and explore or even take up the job as a Ronin or a Traveling Merchant like Kraft Lawrence and Holo from Spice and Wolf or up and just move to another village
Basic Features

Randomly Generated World


Staring Locations:
Village
Empty (have to find a Village)

Crafting


Tools
Appliances
Furniture

Combat
Registered Jobs


Guard (Defend Village)
Farmer (Make Crops for Village)
Miner (Start/Work in a Mine collecting materials)

Having a house to store all the crap you end up hording

Extended

More jobs


Shopkeeper/Smith (make items to sell)
Traveling Merchant (along with horse, cart and fox eared wolf god traveling companion)
Mayor (make you own town)
Teacher

Normal


Dojo Master


Magus (Research and teach magic to others)

Ronin (more or less a sell sword)
Bandit (like a Ronin but you get to raid people)
Pirate (Bandit but with a cool eyepatch and a kickin ship)

Hunger/Thirst/Sleep Levels
Reputation


low rep can get you attacked by guards or thrown in jail
high rep can earn you discounts and favours

Town relations


Town Guard can launch attacks against enemy towns
trading items gotten from one town to another which they don't like can lower your rep as a merchant

Town Law and Order


Lawful Towns people wont have to worry about theft.
the opposite end is Tortuga for pirates/bandits to sell their wares

Different kinds of houses to buy
ability to build your own house (either outside town limits or buy a plot of land in town)


ships will have a generic base but can be built on as if they are moving land

NPC relationships


makes friend to earn favors/gain influence/get discounts/info
for pirates and bandits you can infiltrate a town, get info on guard placements or influence your new "friends" to help weaken a town from within
dating/marriages/children (same sex relationships included)

Quests
Bosses
Different Town Cultures (can limit jobs/traceable items)
Add iconic towns like Konohagakure or Ba Sign Se and add jobs associated with them such as Ninja, Ramen Delivery Guy, Dai Li Agent or Dragon of the West Tea Shop Guy


191: <p>We (me and a vague but definitely real group of users) in the <a href="http://chat.stackexchange.com/rooms/6697/maid-cafe-">Maid Café</a> would like to make some games. If you are interested, ping me in chat or post/comment here.</p>

<p>There are <strong>no limitations</strong>, but consider these things:</p>

<ul>
<li>It should be fun. Pretty sure nobody here likes text-based "Choose your own adventure" genre, Match-3 or Pinball. Ask yourself if you would have fun making and then playing something;</li>
<li>If we want to make a game sooner rather than later, the core game should be short and simple to make;</li>
<li>If we want to make a game at all, 2D is the faster route than 3D.</li>
</ul>

<p>Use answers for game propositions. If you have some other ideas, <a href="http://chat.stackexchange.com/rooms/6697/maid-cafe-">let's discuss them in chat</a>.</p>

<hr>

<h3>Whatever you have in mind, don't hesitate to post it!</h3>

<p>I'm just explaining <em>my personal</em> concerns about starting a collaborative project which often die soon because the goals are too high for project members. Compare the amount of artwork and story writing needed for an average VN and an average arcade game, and you'll see what I mean. But if suddenly a very dedicated group of people appears that want and will make a VN, I'd only be happy for them.</p>

<p>Part of the gig is learning how to use C#, Unity and whatnot for game development.</p>
 19221: <h1>Trajectory shooting game</h1>
<p>example: <a href="http://gamewise.co/games/49267/DDTank" rel="nofollow noreferrer">DDtank</a></p>
<h1>Introduction</h1>
<p>It might be difficult but its my suggestion because I love these types of games. Trajectory shooting game will be like every person will have their own weapon and that player will use that weapon to throw it in the air and kill his opponent by correct amount of strength. Since it will be trajectory motion therefore player can adjust their angle and then throw object to hit their target. Also this game might be calculative one because users have to first calculate the correct amount of power and angle to throw object so that it will hit the target.</p>
<h1>Basic game:</h1>
<ul>
<li>Human vs Computer. Like both players having health and both of them trying to kill each other by throwing objects.</li>
<li>And Human vs Human matches.</li>
<li>Wind system like due to wind the trajectory motion gets disturbed which will make every round different and difficult.</li>
<li>There can be tutorial at starting showing how to play the game and how to improve their skills. It is important for players to learn how to play this game and how to calculate so that they can hit target.</li>
</ul>
<h1>Extended Game</h1>
<ul>
<li>We can use team vs team game match where every team got one chance to attack.</li>
<li>It can be boss level fight. Boss level fight means player have to complete each level to earn level or any item etc.</li>
<li>There can be armory settings like to increase defense and many more.</li>
<li>Restricting the angle for different weapons.</li>
<li>There can be different maps for various matches.</li>
</ul>
 1587: <h1>Murder Game - FPS</h1>

<p>this idea was inspired by one Dark Brotherhood quest in The Elder Scrolls IV: Oblivion. all players are inside a single house and one of them is the murderer who has to pick off the remaining players without being caught.</p>

<p>the murderer is chosen at random and only the murderer will know at first. the other plays win if the catch the murderer. the Murderer will then have # minutes to commit their first kill before the game restarts and a new murder is select</p>

<p>in order to catch the murderer the suspect has to be detained by tying them up and placed in a zone for a certain amount of time until the suspect is taken out of the game. </p>

<p>once the suspect has been removed from the game all players will see what the suspect saw during the time of each murder as such it will be clear what involvement, if any, the suspect had with any murders. the suspect can be freed before they are removed from the game either by other player or themselves (by having a crafted tool to help their own escape)</p>

<p>the game will be in the First Person so that players can see someone approaching from behind unless in front of a mirror and hopefully sound will be close to how it works in real life so that when players "sleep" they see a black screen (or some other animation as if dreaming) but they can still hear (so they can wake up if they hear a strange noise like someone sneaking about)</p>

<h2>Basic Game</h2>

<ul>
<li>Single Map (Mansion Interiour)</li>
<li>Multi-Player Only</li>
<li>Needs (Like Hunger, Sleep, Toilet etc, like in The Sims)

<ul>
<li>this allows the murderer to drug/poison their victims food or try and kill during their sleep</li>
<li>if someone is expect to go take a bath the murderer can rig something up to kill them (ie. plugged in toast falls in)</li>
</ul></li>
<li>Possible list of everyday tasks that players have to do one item on the list every # minutes

<ul>
<li>this prevents players just staying in one room</li>
<li>this forces the murderer to blend in aswell</li>
</ul></li>
</ul>

<h2>Extended Game</h2>

<ul>
<li>Other Maps

<ul>
<li>Estate (includes Interiors and Exterior)</li>
<li>Hotel</li>
<li>Neighborhood (remember the Pint Size Slasher from Fallout 3?)</li>
</ul></li>
<li>Other game modes

<ul>
<li>Hitman - the target is marked and everyone chooses roles. one player is randomly chosen as the Hitman to kill the target.</li>
<li>Death Note (Yes, a use for all those dam <a href="https://anime.meta.stackexchange.com/a/2608/1587">Death Note Puzzle Questions</a>) - using the rules of the Death Note Kira goes to try and kill the players while they must find out who is Kira. may have to tweak the Death Note to prevent mass suicides and add a cool down time</li>
</ul></li>
</ul>
 191: <h2>2D Tower Defense</h2>

<p>Like <a href="http://store.steampowered.com/app/102600/" rel="nofollow">Orcs Must Die</a> or <a href="http://store.steampowered.com/app/65800/" rel="nofollow">Dungeon Defenders</a>.</p>

<p>Basic game:</p>

<ul>
<li>On a pre-made level enemies follow a path to the "End". If just one enemy reaches the end, you lose.</li>
<li>Enemies are generated in small batches. Let's say 1 every second for a batch of 5, with a delay of 20 seconds between batches.</li>
<li>Enemies can be killed by traps that automatically trigger when enemies step on them, and need 10 seconds to reset. Trap can kill all enemies within its trigger zone.</li>
<li>Player can install a limited number of traps throughout the level. Inefficient placement will result in enemies passing through them.</li>
<li>Player can kill all enemies within some range from the cursor, with a significant delay. We'll figure out the game balance in the process.</li>
</ul>

<p>Extended game:</p>

<ul>
<li>More levels with multiple paths, possibly randomly generated from pre-made chunks;</li>
<li>Enemy types resistant to certain attack types (like ice and fire);</li>
<li>Trap types more efficient and useless against various enemy types;</li>
<li>Different player attacks;</li>
<li>Better art and sound? eh </li>
</ul>

<p>If you're interested in this idea, or you want to propose changes, comment below.</p>
 1587: <h1>TCG (Trading Card Game)</h1>

<p>examples: <a href="https://en.wikipedia.org/wiki/Yu-Gi-Oh!_Trading_Card_Game" rel="nofollow noreferrer">Yu-Gi-Oh</a>, <a href="https://anime.stackexchange.com/a/5825/1587">Weiß Schwarz</a>, <strong><em><a href="http://www.tantocuore.com/about.htm" rel="nofollow noreferrer">Tanto Cuore</a></em></strong></p>

<h2>Basic Game:</h2>

<ul>
<li>1 VS 1 with a Computer Opponent</li>
<li>1 VS 1 with Human Opponent</li>
<li>1st Series of cards</li>
<li>In-game slideshow explaining rules</li>
</ul>

<h2>Extended Game</h2>

<ul>
<li>2 VS 2 Tag Team</li>
<li>More Series of cards</li>
<li>Playable Tutorial</li>
<li>Single Player Story Mode(s)

<ul>
<li>Unlocking of more AI Opponents with themed decks/strategies</li>
<li>A new Story Mode for every released series</li>
<li>Tutorial can be integrated into story</li>
</ul></li>
</ul>

<h2>Notes</h2>

<ul>
<li>Card Game rules will need to be discussed (personally i liked Yu-Gi-Oh's approach)</li>
<li>New cards can be added later by players in a similar way to how League of Legends for Forum RPGs allows players to make new Characters</li>
</ul>
 1587: <p>This was an idea for a game i thought up while playing Minecraft and tried to duplicate with mods but couldn't get close. the idea is that you would find a town and set yourself up with a job there whether that be starting a farm to supply their food or working, a guard to protect it or a smith/builder.</p>

<p>with these jobs you have different levels of responsibility ie.</p>

<ul>
<li><p>with the farmer you with just harvest the crops or own the farm itself and handle all the fiances including hiring other farm hands</p></li>
<li><p>with a guard you can just follow your orders or be the town commander and order where your guards patrol</p></li>
</ul>

<p>and later if you don't want to be tied down in a single town you can go out and explore or even take up the job as a <a href="https://en.wikipedia.org/wiki/R%C5%8Dnin" rel="nofollow noreferrer">Ronin</a> or a Traveling Merchant like Kraft Lawrence and Holo from <a href="https://en.wikipedia.org/wiki/Spice_and_Wolf" rel="nofollow noreferrer">Spice and Wolf</a> or up and just move to another village</p>

<h2>Basic Features</h2>

<ul>
<li>Randomly Generated World

<ul>
<li>Staring Locations:</li>
<li>Village</li>
<li>Empty (have to find a Village)</li>
</ul></li>
<li>Crafting

<ul>
<li>Tools</li>
<li>Appliances</li>
<li>Furniture</li>
</ul></li>
<li>Combat</li>
<li>Registered Jobs

<ul>
<li>Guard (Defend Village)</li>
<li>Farmer (Make Crops for Village)</li>
<li>Miner (Start/Work in a Mine collecting materials)</li>
</ul></li>
<li>Having a house to store all the crap you end up hording</li>
</ul>

<h2>Extended</h2>

<ul>
<li>More jobs

<ul>
<li>Shopkeeper/Smith (make items to sell)</li>
<li>Traveling Merchant (along with horse, cart and <strike>fox eared wolf god</strike> traveling companion)</li>
<li>Mayor (make you own town)</li>
<li>Teacher</li>
<li><ul>
<li>Normal</li>
</ul></li>
<li><ul>
<li>Dojo Master</li>
</ul></li>
<li><ul>
<li>Magus (Research and teach magic to others)</li>
</ul></li>
<li>Ronin (more or less a sell sword)</li>
<li>Bandit (like a Ronin but you get to raid people)</li>
<li>Pirate (Bandit but with a cool eyepatch and a kickin ship)</li>
</ul></li>
<li>Hunger/Thirst/Sleep Levels</li>
<li>Reputation

<ul>
<li>low rep can get you attacked by guards or thrown in jail</li>
<li>high rep can earn you discounts and favours</li>
</ul></li>
<li>Town relations

<ul>
<li>Town Guard can launch attacks against enemy towns</li>
<li>trading items gotten from one town to another which they don't like can lower your rep as a merchant</li>
</ul></li>
<li>Town Law and Order

<ul>
<li>Lawful Towns people wont have to worry about theft.</li>
<li>the opposite end is <a href="https://i.stack.imgur.com/gUfY7.png" rel="nofollow noreferrer">Tortuga</a> for pirates/bandits to sell their wares</li>
</ul></li>
<li>Different kinds of houses to buy</li>
<li>ability to build your own house (either outside town limits or buy a plot of land in town)

<ul>
<li>ships will have a generic base but can be built on as if they are moving land</li>
</ul></li>
<li>NPC relationships

<ul>
<li>makes friend to earn favors/gain influence/get discounts/info</li>
<li>for pirates and bandits you can infiltrate a town, get info on guard placements or influence your new "friends" to help weaken a town from within</li>
<li>dating/marriages/children (same sex relationships included)</li>
</ul></li>
<li>Quests</li>
<li>Bosses</li>
<li>Different Town Cultures (can limit jobs/traceable items)</li>
<li>Add iconic towns like <a href="http://naruto.wikia.com/wiki/Konohagakure" rel="nofollow noreferrer">Konohagakure</a> or <a href="http://avatar.wikia.com/wiki/Ba_Sing_Se" rel="nofollow noreferrer">Ba Sign Se</a> and add jobs associated with them such as Ninja, <a href="https://www.youtube.com/watch?v=wRC_iNWt7kM" rel="nofollow noreferrer">Ramen Delivery Guy</a>, Dai Li Agent or <strike>Dragon of the West</strike> Tea Shop Guy</li>
</ul>
