Ikea hacking never gets old, but this goes beyond your average mod: An interaction designer named Marc Dubois has taken three cheap-o Ikea products and modified them to act as controllers for desktop games.
Razer's Hydra PC gaming controller is taking the guts from two Wiimotes and packing them into the form factor of its nunchuck accessory. They say it's the first "gaming-grade" motion controller.
The video doesn't delve too deep into how the gun works, though the basic mechanics are fairly evident. The gun depends on an accelerometer (or similar device) to determine its orientation, which is seems to relay as a raw mouse/keyboard signal, hence the "no drivers" claim.