In your opinion, what is the 1 movie that everyone should see by the time they're, say, 18?

This is not necessarily your favorite movie or the movie you grew up with or the movie with the highest critical acclaim that you've seen, but it can be any one of those. This is the movie that you don't hesistate recommending even though you're not completely positive the person is going to like it as much as you do- they should still see it for what it's worth.

And why should everyone have seen this movie?

I'm really interested to hear what you all say, and even though I love lists please don't give me a list I just want ONE movie in your reply. I don't want this to turn into a top 5 favorite movies list- there are other threads for that.
I know this may be hard because I don't have an answer myself yet.
I'm thinking...

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he ate my heart then he ate my brain

I'm gonna say "Spun". You walk away feeling like you just did meth. Plus you the get the whole fucked-up-life experience with out really having to do it.

fame is the movie i came up with,it's a lively movie, and i think this movie will have positive effects on young people,because after seeing this movie,you will feel so full and no fear of following your dreams~

I haven't seen either of those:/. They're on my list.

I should clarfiy that the one movie should be a movie that when people say "I haven't seen _____" it makes you go .

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he ate my heart then he ate my brain

the breakfast club
i really wish i had seen it when i was a teenager