WiiSaber
Remember MacSaber, the little program that turned your Mac portable with motion sensing into a lightsaber (well, at least made it sound like one whilst you were wildly swinging it around)? I know some people, like me, were a little wary of swinging around their portables for fun and that is where WiiSaber comes in.
Get your Wiimote (which comes with Nintendo's Wii), add a Mac, and now you can swing your Wiimote around like mad and pretend you're a Jedi.
Thanks, Ian.