Double Pendulum: http://physicstoys.blogspot.com/p/physics-toy-store.html Chaotic motion from a simple assembly of two physical pendulums (one attached to the end of the other) with the energy of the system moving frenetically back and forth between the potential energy of gravity to the kinetic energy of motion. Chaotic motion is characterized by extreme sensitivity to initial starting conditions, tiny differences in how the system is released leads to dramatically different outcomes each time.

They’re Quackers … but also fine examples of a double compound pendulum | The House of Automata