Director John Carpenter and sci-fi writer Dan O'Bannon cobbled together this sci-fi treasure with buddies on a meager budget early on in their careers. From Wikipedia:
In the middle of the 22nd century, humankind has reached a point in its technological advancement to enable colonization of the far reaches of the universe. Armed with artificially intelligent "Thermostellar Triggering Devices", the scout ship Dark Star and its crew have been in space alone for twenty years on a mission to destroy "unstable planets" which might threaten future colonization.
UPDATE: Looks like youtube pulled the video, so I've replaced the full-length with the trailer.