You guys have GOT to see this!
http://www.theprodukkt.com/kkrieger.html#dload
It's called KKrieger. It's a 96K 3D fps that'll give HL2 a run for it's money... well, maybe not. Still, the game looks amazing... just try it and tell me what you think!
PS: Extract it first from the ZIP file; otherwise, you'll expierience slowdowns. I think it has something to do with the ultra-compressed files.