El Topo
The greatest thing about that movie for me is watching how others respond to the scenes.
I love the movie, but it's even more fun to gather how it's recieved.
Edit: I guess to be on topic, randomly remembered some fun movies I enjoyed a while back when my laptop died, causing me to enter a Netflix craze.
Bronson
How to be a Serial Killer
Conspiracy Theory
The Perfect Host
Primer
Visioneers
Pi
When I first watched it when I was younger I wasn't really aware of the whole pain lust thing, so I watched it a bit more confused. It being framed like a typical love story with some atypical aspects to their preferences did help in understanding it.
Once I stopped fearing and embraced the kinks I have, the film's nature changed drastically.
It was that sharp divide that had me love showing it to other people. Watching if they winced or grinned at some parts, who they claim to relate to from the film, how they feel about how the love triangle sorted itself out, it's lead to some fun discussions that have been very telling.
Hesher was pretty awesome - a delightful mix of strange and humorous.