In the past few years, we have covered plenty of cool kinetic ball clocks here. The Congreve Rolling Ball Clock is pretty special though. It uses a ball rolling along a zigzag track to keep the time. It was originally invented by Sir William Congreve in 1808.
As explained on Wikipedia:
The ball takes between 15 seconds and one minute to run down the zigzag track, where it trips the escapement which in turn reverses the tilt of the tray and at the same time causes the hands of the clock to move forward.
Congreve Clocks are pretty rare but show up on auction sites once in a while.