Motorized propeller beanie
What self-respecting nerd wouldn't have one of these things lying around? Originally, I wanted it to be solar powered, but I had to settle for AAA batteries. I scavenged the motor and propeller from a 6 in 1 educational solar kit. There's no reason why you can't print your own propeller and use a motor from a cd player or really any motor.
Print with 0 infill and no shells. Use drill press to make the hole for the motor. Connect wires, add on/off switch if you want, glue everything up in the beanie. Represent nerdom.