A couple months back a Minecraft enthusiast/do-it-yourselfer figured he needed improved seccurity in his apartment. "Unfortunately for me my building does not allow dogs so a big scary animal was not an option," he writes. Then, boom! he got this idea.
A little crude, but Chris' Arduino-powered, motion-detecting, RC-scootering, ssssss-booming Creeper from Minecraft does the trick. Especially if the trick is pissing you off after a hard day's work. Inside the cardboard shell is a speaker, a Wave Shield that plays back two sounds (the fuse, and the requisite bang) and the Arduino-powered guts, mounted on the chassis of a $US15 remote control tonka toy he got at a local drugstore.
It's an entrant in Instructables' game.life Challenge, so if you find it useful or funny, give it a click there, too.
Motion-Activated Attack Creeper [The New Hobbyist]