The first piece of software we tried with our new custom mini-computer was the classic first person shooter 'Quake 3' for a little game play. This involved compiling the game to play on Linux which meant grabbing Linux targeted source code through a Dropbox like service we found. This link
shows the lines of code used to install Quake, installing the necessary Linux packages, and building a Quake directory.
Raspberry Pi running Quake 3
We also downloaded the popular game Minecraft with a few simple lines of code. This meant simply downloading a user made version of the game and dumping it into a directory via LXTerminal. The team behind the Minecraft Pi edition has created a website for their version on the game here
Minecraft Pi Edition running on the Raspberry Pi