A quick, and admittedly stupid game I set up while bored. It consists of a thumb tack-toothed "cobra" attached to a very aggressive servo, which is driven by an ultrasonic distance sensor. The closer you get, the angrier the snake gets! Watch yourself friends!
(Please don't try this at home, work or in Radio shack with sharp objects. They didn't think it was funny. Also, the tack was slightly dulled in order to avoid blood-born illness transfer between friends... I thought of everything!)