In Warhammer 40K Servo-skulls are robotically enhanced skills that hover behind their owners. They are used in lots of ways; from a simple floating torch all the way through to Inquisitors using them as Familiars.
The Deviant Artist Spooky 777 has taken a medical skull model and given it the Warhammer 40,000 treatment. This is an impressive, real life, Servo-Skull.
The Warhammer 40,000 wiki has a whole page on the servo-skull which contains this picture. It shows what a good job Spooky 777 made of the conversion.
Via Obvious Winner