MacSaber might be the coolest use of motion sensor in some Mac portables ever. Simply install this beta, and swing your MacBook (or other laptop) around. Suddenly your laptop is a laptop no longer, nay, it is a light saber!
I must admit that I almost threw my MacBook across the room fooling around with this, but boy is it fun.
Update: To clarify, to the right is a screenshot of the program running. Swing your MacBook around, and make sure your speakers aren't muted.