Solaris

It's now been some years since I last watched it. Still, I can't get rid of the impressions of emptiness, absurdity and impossibility to understand (the world, and the human mind) that this movie left into me. It can be violent to your mind, without showing a single violent image (by the way, I often see this movie as a counterpart to Clockwork Orange, even more than to 2001). It can stun you, with ten or twenty minutes of incomprehensible silence. It can deprive you of any certainty in the laws of nature - such as, people only die once - and thus leave you vulnerable and naked.

I know that many friends to whom I've shown this move did not understand it. So I'm not saying you'll like it. But this is possibly the best (non-action) sci-fi movie ever made.

Watch it at night, alone, when everything out of your home is dark, silent, and cold.