What's the most famous science fiction movie you've never seen?

No matter what a movie addict you are, chances are you've got some gaps in your knowledge. There's probably at least one movie that all your friends have seen that you've never watched, for some reason. Maybe you never got around to it, maybe your friends described it so much, you no longer felt the need to see it. Chances are, there's at least one movie you're secretly ashamed of having skipped.

So it's time to come clean — what's the most famous movie you've never seen? I'll start: I've never seen Jurassic Park.