Cool idea for a thread, Hedge. Hahaha@ my faves you pointed out. This was hard for me to narrow down to five *other* picks besides the ones Hedge already pointed out for me (I also have honorable mentions). Anyway, I think the following are probably the top 5 movies that made me think the most.

5.
Dawn of the Dead - no, it's not the deepest movie ever and it has its fair share of schlocky zombie fan-service and gonk humor. However, the themes regarding consumer culture, the collapse of society and how people can become more of a threat than any monster are as relevant today as when this classic movie debuted.
Night of the Living Dead deserves its spot as one of the most highly regarded films of all-time, but I think
Dawn is the more consistent film with more to say overall.
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4.
Grave of the Fireflies - When it comes to sad movies, this is probably one of the saddest I've seen. Yes, it's animated, but it still manages to be one of the most heart-wrenching things put to film that I've ever seen. The movie focuses on the effects of WWII bombing on people in and around Tokyo, particularly children. The film is careful not to paint anyone or country as good guys or bad guys. The main message is what terrible things war can do to civilians. The imagery, music and main characters are tragic through and through. This movie will absolutely crush you.
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3.
A Clockwork Orange - Like Hedge, this film got me thinking like few others. There's a timelessness to the film on one hand, but on the other, the visuals of the film have aged so strangely (note: *not*
poorly) that its developed a fine retro-futurist absurdity that just can't be replicated. The elements of an undeniably likeable Robin Hood or Peter Pan type character (Alex) being so depraved and twisted into a completely self-serving and degenerate monster are still compelling. Free will, social justice, criminal reform and mind control are all given a bizarre, but thoroughly entertaining trip through the wringer. The unique take on language and slang is also extremely interesting to me.
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2.
Taxi Driver - Another psychologically messed up main character, Travis Bickle is a pretty strange dude. He presents himself as an "awe shucks" nice guy and seems like he might just get the dream girl of the movie, but then takes her on a date to a XXX porn flick, thinking it's as normal as watching Harry Potter. He develops all sorts of unhealthy attachments to women (and girl prostitutes) he has no business going after. He has strong populist opinions about "cleaning up" NYC and becomes somewhat interested in politics only to get extremely close to assassinating a candidate for governor. Travis falls far and gets to the verge of a murderous rampage and ends up acting on it. His motivations are an uncomfortable mix of murderous obsession and heroism, exploding in bloody violence. The best twist of the movie is how Travis is perceived in the media following his meltdown - it vividly shows how blurry the line can be between hero and villain.
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1.
American Psycho - Before he was Batman, Christian Bale portrayed Patrick Bateman, a wildly successful businessman of the 80s that worked the night shift as a psychotic serial killer who loved to do all manner of terrible things to vulnerable prostitutes. While I'm well-aware that this was a dark comedy now, it took me a little while to catch on. I remember watching it for the first time and my thought process being "this is fucked up, so messed up, wait a minute... it's actually kind of funny!"
American Psycho walks on the knifes edge of many lines. I can see how the film could be used to glorify sexual violence against women, but that's not the point of the film. I'd like to say "clearly not the point," but I'm not sure if it is clear. Some people may not get that this film is supposed to be a satire and no one is supposed to see Patrick Bateman as likeable in any sense of the word. The scene where Patrick is screwing prostitutes while staring at himself in the mirror as "Susudio" by Phil Collins blares in the background is one of the most hilarious scenes I've ever watched. Also, this is one of those films with a sudden, but great ending that leaves much to interpretation.
Honorable mentions:
Adaptation
Black Swan
Donnie Darko
Inception
Stranger Than Fiction