Daniel Rojas created this impressive “laser target-finding, self-reloading multi-shot rotary rocket launcher” using LEGO blocks. Three videos after the jump.
On top of all sits the feeder mechanism, which consists of a reservoir for up to five rockets and a feeding motor that delivers them into the launch bay. The long black rails are the ones on which the rocket comes out. The trigger mechanism (behind the yellow liftarms) pulls back a hammer and loads two rubber bands. These pull the hammer forward, hitting the rocket and firing it. The red plates are part of the tilting mechanism, which was disabled in the final build. The entire structure sits on a turntable allowing a pivoting action
(Thanks, Will T)