Oldboy - an awesome movie (open spoilers)
THIS is why I love Netflix. I never could find movies like this in Blockbuster or what have you. I was wrapped up in this movie from start to finish.
I don't even know what to say other than how much I liked it. As Ebert said, it's not about the violence, but about the depths of the human heart it lays bare. When a movie even makes you feel bad for a depraved psycho, that's something.
This isn't a movie for the light-hearted, so I won't recommend it to just anyone. It is excellent catharsis, so if you like that sort of thing, I highly recommend.
Beware! An octopus dies in this movie. If you're like me and know how intelligent the little guys are, it will bother you - but you can just wince during that scene and it never comes up again.