Check out this clever weight-driven kinetic sculpture. The marble moving through the tracks cause the box to rotate, which acts as as type of escapement.
From the creator:
The thread connecting the two weights is wound around a reel on the axis of the front part. As one of the weights is heavier, the front wants to rotate. Where the marble reaches the "bottom", there are two levers. These levers prevent the machine from spinning while the marble is on the track, and release the machine every time the marble hits one of them. The levers also work as a ratchet mechanism to allow easy winding up. The marble probably feels a bit like Sisypho
[ Thanks Felix! ]