CamSpace - any game, any webcam
Watch the video! This really makes me excited for all sorts of reasons. First, it is free, the only thing you need is a webcam and then anything lying around your house will work for a controller.
Second, it allows the player to innovate in ways to control the game, as opposed to the controls being restricted to mouse / keyboard, and what the developer has set.
THIRD, it's just plain awesome. AWESOME.
Discuss experimental games / gameplay.