Algodoo

Perpetual motion. Requires 2 attractive circles, one fixated, and one hinged to a circle of the same collision group.

Additional speed can be achieved through heavier or more attractive centre circles.

Give this one a bit of a spin, and it will accelerate up to ~83 rads/s on the default frequency. A higher frequency allows a greater speed, but also reduces the acceleration. Vice versa for lower frequencies.