PrBoom is a cross-platform version of the classic 3D first person shooter Doom from id Software. Originally written for PC, PrBoom has been lightly modified to run on GP2X. Release notes:

PrBoom 2.2.6-beta3 is out. Joystick directions are now mapped to keys and Vol-/Vol+ are used for weapons cycling.

http://www.gp32x.com/board/index.php?showtopic=24932