Which commanders benefit from being in the Command Zone other than Oloro?
13 possible commanders interact with the command zone in an unusual way. 8 commanders have abilities that function in the command zone. All of them were created for the preconstructed commander decks or released in commander specific sets. They even eventually created the &quot;Eminence&quot; ability word for  abilities that function in the command zone.

Arahbo, Roar of the World has the ability &quot;Eminence — At the beginning of combat on your turn, if Arahbo, Roar of the World is in the command zone or on the battlefield, another target Cat you control gets +3/+3 until end of turn.&quot; giving you a free boost to one attacker each turn.
Derevi, Empyrial Tactician has the ability &quot;: Put Derevi onto the battlefield from the command zone.&quot; This lets you play the commander without casting it, so it cannot be countered as a spell (but as an activated ability, with Stifle) and avoids the commander tax* so it will always cost 4 mana.
Edgar Markov has the ability &quot;Eminence — Whenever you cast another Vampire spell, if Edgar Markov is in the command zone or on the battlefield, create a 1/1 black Vampire creature token.&quot; giving you creature tokens for playing tribal vampires.
Inalla, Archmage Ritualist has the ability &quot;Eminence — Whenever another nontoken Wizard enters the battlefield under your control, if Inalla, Archmage Ritualist is in the command zone or on the battlefield, you may pay . If you do, create a token that's a copy of that Wizard. The token gains haste. Exile it at the beginning of the next end step.&quot; allowing you to get a token copy of your wizards for one turn, potentially triggering ETB effects or letting you use their tap abilities earlier.
Liesa, Shroud of Dusk - Liesa has the ability &quot;Rather than pay  for each previous time you've cast this spell from the command zone this game, pay 2 life that many times.&quot; forcing you to use life instead of mana for the command tax when casting her.
Oloro, Ageless Ascetic - Oloro has the ability &quot;At the beginning of your upkeep, if Oloro, Ageless Ascetic is in the command zone, you gain 2 life.&quot;
The Ur-Dragon - The Ur-Dragon has the ability &quot;Eminence — As long as The Ur-Dragon is in the command zone or on the battlefield, other Dragon spells you cast cost  less to cast.&quot; effectively making him a Dragonlord&#39;s Servant on or off the field.
Yuriko, the Tiger&#39;s Shadow - Yuriko has &quot;Commander Ninjutsu &quot; functioning like ninjutsu from Kamigawa. This lets you bounce an unblocked attacker to put Yuriko into play. Like Derevi, this is not casting, so you will not pay commander tax.

Currently 5 other possible commanders interact with the command zone in an unusual way, but not through an ability that works there. None of them require the creature be your commander :

Captain Vargus Wrath - gives +1/+1 to all pirates (himself included) when he attacks for each time you have cast your commander from the command zone. He doesn't need to be your commander for this effect.
Jeska, Thrice Reborn - her starting loyalty is the number of times you have cast your commander this game. She does not need to be your commander for this effect.
Jirina Kudro - creates tokens when she enters for every time you have cast your commander this game. She does not need to be your commander for this effect.
Reyhan, Last of the Abzan lets you put counters on creatures when another creature with counters dies or when it is returned to the command zone.
Tevesh Szat, Doom of Fools - Puts all commanders onto the battlefield under your control, taking them from other player's fields or their command zones.

There are also many other cards that interact with the command zone but can't be commanders, most with effects that scale based on the number of times you have cast your commander or move your commander out of the command zone into your hand or onto the battlefield.

* This is the cost increase for casting your commander from the command zone again every time it is sent back to the command zone.
With a recent rules change, commanders die like normal creatures before being moved to the command zone. This means Reyhan's ability handles dying commanders like it handles all other creatures. Commanders being sent to the hand or deck will still work as before, those replacement effects are unchanged. A commander being exiled will not trigger Reyhan anymore, since they are sent to exile as normal and then they are no longer a creature you control when they are sent to the command zone. This is still true of Skullbriar, the Walking Grave who, while he keeps his counters moving between zones, is not a creature you control when in the graveyard or exile, and won't trigger the effect a second time.