Not only does Wolf3d run beautifully on the iPhone, the controls (and options for modifying them) actually make the iPhone a viable platform for 2.5 dimensional FPS games.
I'd like to see what he can come up with for Quake (a fully 3D shooter - which adds aiming up and down)
You'd need some kind of giro for the z-axis. Right now the iphone can only tell if it's facing uyp or facing down, but can't tell by what degree. Maybe in later edititons they will make the z-axis giro like the others. Alternatively, you could make a device you can attach to the iphone that tells it its position along the median plane.
I'd like to see what he can come up with for Quake (a fully 3D shooter - which adds aiming up and down)