Cable car that automatically stops at the station.
DC motor is used to move the cable onto which a (paper) cable car hangs. The light sensor is set very sensitive before the motor. When the cable car approaches, its shadow falls onto the light sensor, and the motor stops.
See video: Simple cable car: http://youtu.be/qjQP_srBJNA
I don't have the bits to reverse the motor direction, which means that once it is down, you have to manually put it up again.