A version of q3cz Quake 3 has been ported to the iPhone. Players can wirelessly challenge other iPhone/Touch users to a mobile deathmatch by using the uilt-in accelerometer to move around and by tapping the screen to shoot. The movement in the video seems very basic (comparable to just using a keyboard), but it's probably more fun than playing java Tetris.

The blog of the creator of the video can be found here.