The Mysterious Rattleback is a tricky toy.
Spin it counter-clockwise and it continues to spin.
When you spin it clockwise, it will suddenly stop, rattle back and forth, and then spin slowly in the opposite direction.
You can also tap an end and it will spin around automatically. It's interesting to ponder how this act of physics really works, but it is also fun to simply enjoy the astonishing behavior of the Rattleback.