devastation328

I saw that cube is available for pocket pc now. As i recall, it's an open source first person shooter so you might try taking a peek at the source for that or just mod it.

/edit

just remembered... irrlicht, anotehr open source 3d engine will supposedly get pocket pc rendering. I saw a video of it a whiel back. It runs slow, and you're obviosly not going to be able to do steep parallax mapping, stenciled shadows, and environment mapping, but it's worth looking into.