"Silent Running" is one of my favorite cult films.  This is a powerful environmentalist film from 1971 starring a young Bruce Dern.  The Earth has created domes in space to preserve the forests from polution or a possible nuclear war.  Bruce Dern is a forest ranger on a spacecraft taking care of the domes.  When he is ordered to destroy the domes by the government, he rebels and kills the other rangers in self defense.  Three drones called Drone 1, Drone 2, and Drone 3, are reprogrammed by Dern to respond to Huey, Dewey, and Louie.  A powerful scene in the film is when one of the drones is careless outside the spacecraft, and is swept into space.  Another drone finds the lost drone's foot still attached to the craft, and Bruce Dern's character scolds the other two drones by telling them "that's what happens when you are careless!", trying to teach the remaining two to be careful.  These robots are silent, but are loaded with innocent charm and personality.  Please see this film if you are a robot fan!

Links:
Silent Running Drones by John Rigg
SF Movie Heaven
Robot Builders.Net