It's cute, It's polite and it is really deadly. It's a turret from Portal. It moves, has light, has sound, and something that my previous Portal project did not have: Camera tracking.
The turret is controlled with an Arduino and a PC. The arduino handles the movement and the light, the PC processes the video from a webcam to decide where the turret needs to aim and provides the sounds for the turret.
When no computer is present, the turret automatically switches to manual control. In this mode the turret can be controlled by a joystick, though there will be no sound.
The turret is full 3D printable and requires very little additional tools to make. This does not mean that this is an easy project, but it is manageable with some basic 3D printer, electronics and programming skills.
For more projects like this, go to my site: http://ytec3d.com/