I'm not huge Crysis fan (then again, I haven't played it yet), but I thought this might interest a select few of you: Wiisis.
Requirements
1. Nintendo Wii Remote
2. Nintendo Wii Nunchuk Controller
3. PC Bluetooth Adapter
4. Crysis (Obviously)
Note: Not all Wii Remotes are compatible with all Bluetooth adapters. I suggest you not buy Wii Remotes for this purpose alone. Also, sensor bar is optional.
I don't know how Crysis' anti-cheat measures work, but I assume that because this is a direct modification of the game it wouldn't work, or would be limited to play with other Wiisis players. Still pretty neat, though.