A Clockwork Orange
Stanley Kubrick strikes again with this head-scratcher. The film takes a darker turn than the book. After a suicide attempt, he undergoes conditioning to make him a "happier" person. He soon returns to his manic and destructive ways. There's no happy ending.
2001: A Space Odyssey
The ending of this film has viewers guessing at what happened. Did Bowman really get sent back to Earth with new powers, or did he get stuck in some sort of trance by the super-beings that kidnapped him? Stanley Kubrick has said that he was sent back to Earth, but what happened there is up to the viewer to decide.