On of our favorite devices around the office is a small solar-powered airplane that hangs above the workbench. Every so often, it spins up the propeller, and zooms around in circles!

Build your own with a Grand Wing Servo GWS GW/EP3030/BK 87mm Dia x76mm pitch (3.4" x 3" pitch) propeller, which is used very successfully in by  "indoor flyer" remote controlled aircraft.

The hub has a 1.5mm hole (0.059") which matches many suitably-sized motors, like our RM1a motor.