BEAM robots

First thing's first, a "BEAM robot" is not a robot!
BEAM robots are clever combinations of circuitry and mecanics that act like bugs or simple robots.
They are not programable and they have no real way of sensing the world.
They are, however, a good way to impress teachers at school.
Because of this I have included some of them below: 

Wall Following Mouse

Trimet/Symet