No, seriously, I think a lot of Terry Gilliam's work like Baron Munchhausen, Brazil, Time Bandits and Fear and Loathing are great mind-**** movies. Stanley Kubrick's work as well with 2001, The Shining, and even Dr. Strangelove has some great subtle details that make you think. And you can't forget about Blade Runner.
A lot of Aardman Animation's earlier short films before Wallace and Gromit and Chicken Run are very out there, especially Ident.
I honestly couldn't be bothered with the four or five times you'd need to watch that film to actually get it, so I just googled it after first attempt. It's actually a pretty clever story, but omitting a bunch of scenes necessary to follow the narrative and having the entire dialogue take place in technobabble, I just found aggravating. I thought Upstream Colour was a much better film.
That is the quintessential example. Each time you go over it in your head thinking you've unlocked the story you come to an inexplicable paradox. It's masterful in that way.
I'm assuming everyone is talking about the original 2003 version of OldBoy since the comments predate the Spike Lee 2013 release. Has anyone seen that one? I honestly never heard of it, but watched the trailer and it looks good.
this movie.....if there was ever a movie it would be a treat to unsee it would be this POS....remember back in college a wanna be cool so called friend recommended it ....oh it's so artsy so cool you have to see it....it was as much disgusting as it was disturbing garbage
Enter the Void by Gaspar Noe I found interesting. Very much an endurance test like Irreversible, and a bit overly long in parts, but I still enjoyed the themes tied in with death and mind altering substances.