A small, solar powered wind turbine. I've printed the parts with PLA. You don't need any glue - just a piece of sandpaper. The tower is made out of two pieces to be printable even for smaller printers. The connection is stable enough to prevent any sort of wobbling.
These parts fit perfect:
I've connected the motor with two solar panels (parallel) for the inrush current. You can use a bigger panel (with max. 5V).
Model in action: https://www.youtube.com/watch?v=Z9UengZrGjU