This is the number one source for all your GP2X needs.
D1X-Rebirth is an adaptation of the engine from the DOS game Descent ported by Zico to the GP2X. It runs very nicely at 250mhz with sound.
Descent is a 3D first-person shooter video game noted for popularizing the use of true 3D rendering technology and providing the player with six full degrees of freedom to move and to look around.
The GP2X wiki. A complete guide to Gamepark Holding's handheld game and media player, developed by the GP2X user and developer community.