This neat little hack turns an NES controller into a Keyless Entry System. The controller snakes from a wall-mounted Arduino: the rapid-fire entry of the Konami code (or similar NES input) will lock or unlock the door via a CD-ROM ejection mechanism that pushes or pulls the lock, with failed entries triggering a snapshot of the face of the would-be infiltrator. Not exactly subtle decorum, but very, very geeky.
Nintendo Keyless Entry System [Instructables]
A guy here in Portland (Paul Stoffregen) made a door lock like this (but used an actual solenoid door lock) to get into the games area at Free Geek.