Gyroscope
A gyroscope is a device with a spinning disc or wheel mechanism that harnesses the principle of conservation of angular momentum: the tendency for the spin of a system to remain constant unless subjected to external torque.
A gyroscope is probably one of the most fascinating physics toys and one of the most useful applications of conservation of angular momentum in several branches of science and technology https://twitter.com/Rainmaker1973/status/1689259533078548481