Meet Space Wheel by Andrews Mfg: a magnetic desk toy that creates the illusion of perpetual motion. It has a wheel that keeps going back and forth without slowing down. The trick is the motor inside the base that makes it happen. Without the battery, the wheel comes to stop after a couple of minutes.
Space Wheel was originally made in the mid 1970s. It is rare but you can still find it on auction sites on eBay.