Unity and GNOME has nice app launchers by default. However, at any point of time if you get bored by the default app launcher for either of them, feel free to pick one from the below list of best app launchers for Ubuntu.
Docky is a full fledged dock application integrated fully with GNOME desktop. It provides an application launcher and docklets like CPU monitor, weather report and clock.
You can create more than one Dock and there are some predefined docklets which you can add to each one of them. You can also drag and drop an item to docky. There are options to increase / decrease icons size, choose transparency and 3D effects.
Ulauncher is another great App launcher for Ubuntu and other distribution. It provides instant search results and an application can be run by typing the name in the search box. You can search files or directories by starting with /. You can search Google directly and there are various other helpful features.
You can grab a DEB file from here or install through the official PPA.
Plank claims to be the simplest dock on the planet with doing just what a dock should do. The interface is pretty simple and so is the configuration. You don't have fancy features here which is the primary reason why it is a very light weight application.
You can drag and drop any application from the Dash Search to Plank Dock.
GnomeDO is fee and open source application launcher for Linux which allows you to search for items from your system or web. You can send emails, play music and get notified when one of your friends post something on Twitter. You can search your Google contacts and control playback music.
DockbarX is a lightweight application launcher for Ubuntu and other Linux distributions. It resembles to Windows 7 task bar and its grouping feature. Latest release has added support for media player control for all music players.
It can be run standalone and actually a fork of dockbar licensed under GPL3.
Do you use any application launcher or the default Unity Dash or GNOME menus are sufficient for you? Let us know in the comments.