Johnny Chung Lee's 3D headtracking software is incredibly cool (skip ahead in the video to the good bits), and the Wii acceleration monitor is a neat trick.
Editorial note: Whoa! You've found a super-old post here on BuzzFeed, from an earlier era of the site. It doesn't really represent where we are anymore, and may in fact be totally broken, but we're leaving it up as a part of our early history.