Well, the usual disclaimer that the list is not especially ordered.
1. Pulp Fiction (1994, dir. Quentin Tarantino)
I consider this movie one of the perfect expressions of American Cool. For this reason, everyone loves to love this movie. But I don't care. This movie change the way I look at storytelling, dialog, and cinematography. It did with negative spaces and silences what many movies can't do with pages of words and action. During the diner scene at Jack Rabbit Slim's, there is a moment when both John Travolta and Uma Thurman are silent. They just smoke, and look off into the distance. It's not awkward, or strange, or forced. It's just one of the coolest shots in American movie history.
2. Amelie (2001, dir. Jean-Pierre Jeunet)
Right? This is the perfect romantic comedy. I assume that upon finishing this movie, Jean-Pierre Jeunet dropped the mic and walked off the stage. On top of that, it's gorgeously shot, meticulously written, and superbly acted.
3. Animal House (1978, dir. John Landis)
This movie is such a legend, every college comedy since then has tried to be it (and failed utterly). It is juvenile a thousand times over, which is why it's so brilliant. It is always immensely gratifying to watch a group of extraordinarily talented people do their best and just not give a fuck. Best of all, instead of insightfully addressing the subtleties of human condition, or whatever, they do this.
4. Predator (1987, dir. John McTiernan)
The first one - accept no imitations. It's Arnold doing what he does best - wearing makeup and punching things with bullets - and so much more. It is also a surprisingly (*) intelligent examination of militant masculinity and the hunter / prey duality. Both the soldiers and the Predator go through the hunter-to-prey transformation. What's more, they actually have clear and interesting psychological responses. All of this - in an 80s Arnold movie.
(*) I'm pretty sure it was surprising even to the writers, as they are the brains behind such incredible follow ups as Wild Wild West and AVP.
5. Requiem for a Dream (2000, dir. Darren Aronofsky)
It is such a brutally beautiful examination of life's downward spiral, it left me in a deep depression for several days. Then someone told me that Trainspotting was even heavier, and today, ten years later, I still can't bring myself to watch Trainspotting. This movie is simply flawless.
6. Ink (2009, dir. Jamin Winans)
This is an obscure indie that seems to have started out when someone wanted to make a mediocre martial arts demo tape. Then this somehow snowballed into an amazing concept and a final reveal that - even though you can probably see it coming - leaves you sobbing like a goddamned child.
7. The Dead Poets Society (1989, dir. Peter Weir)
Maybe my love of stories about alienation and self-discovery are a commentary on who I am. The first time I saw this movie was in English class, just a couple months after moving to the States. I'm sure I didn't actually understand much of it, but it hooked me. There's a measure of great acting and directing.
8. Funny People (2009, dir. Judd Apatow)
Maybe this movie doesn't mean as much if you've never done live comedy. It's a good, honest, true portrayal of what it's like.
9. Rosencrantz & Guildenstern Are Dead (1990, dir. Tom Stoppard)
Alright, Tim Roth and Gary Oldman are two of the best, easy. Tom Stoppard's intelligence, however, is frightening in its reach and depth. This is surely one of the smartest plays there is. It simultaneously filled me with wonder and made me feel like the least dullard.
10. Ghost in the Shell (1995, dir. Mamoru Oshii)
The first time I saw it, I was going through some particularly low and difficult times. It was a bizarre and exhilarating experience to see my mood so perfectly expressed on the screen. I think to this day the effect hasn't really lessened on me.