The Threw-Itself-Stones-In-Its-Way-Machine 2004

The Threw-Itself-Stones-In-Its-Way-Machine is a machine that switches itself off by pelting its off switch with balls.

 
When you press the on button, a ball gets lifted up to a labyrinth where it rolls slowly to the center. There a magnetic arm takes the ball and puts it into a small spoon that lards it along the whole machine towards the off button. If the ball hits the button, the machine stops, if not, another ball gets lifted up to the labyrinth.