The Hexbug is a very cleverly designed, tiny toy robot bug. Out of the box, it has pretty limited functionality.
Once removed from its package and switched on, it marches forward until its antennae bump an obstacle. It walks forward until its antennae bump something, then it backs up and turns left. It then does a reverse-right turn, and continues forward again until the next obstacle. A loud noise (like a hand clap) will also cause it do its reverse-right turn.
The final result, though still only able to turn one direction, is much more robust. They discuss the ability to add numerous sensors as well as pre program different behaviours and personalities.