18. 2001: A Space Odyssey

Almost all of Stanley Kubrick’s filmography was left wide open to interpretation, so it was only natural that the climax of 2001: A Space Odyssey would generate so much intense discussion and debate.
In short, lead character Dave winds up on Jupiter, discovers a highly advanced alien species, ages decades in a matter of moments, dies and is reborn as a star child. It’s wild, bonkers and totally existential, which is exactly how Kubrick wanted it to be.
Never one for spoon-feeding viewers, in subsequent interviews the filmmaker proceeded to clear up absolutely none of the mystery, insisting that it’s entirely up to personal preference and interpretation.