RobBob is a 2 degree of freedom robot head that is powered by bevel gears! Spin one knob and robBob's head turns. Turn the knobs together and robBob will tilt his head up and down.
You can add some servo motors and an arduino board to give RobBob some life!
This video show the engineering process behind RobBob.
The files are available for both the mechanical version as well as the servo powered version. You can find info on how to make the servo version work here
Recommended print settings: Layer Height: 0.2mm Nozzle: 0.4mm Infill: 15-18% Filament Use: ~100g