Into the Void (Gaspar Noé, 2010). Not quite as grueling as it sounded, and not that much strobe, thankfully. The most interesting thing about it is that at the base of all the trippiness and squalor is a sentimental idea, which Noé lays out by repeatedly giving us guidelines for watching the movie we’re watching.
House (Nobuhiko Ôbayashi, 1977). Also trippy. About midway through, the cat begins playing the piano and meowing in tune, and then you pretty much go with it.
Colossal Youth (Pedro Costa, 2008). Very tricky to blend an arty kind of stylization with a documentary-esque survey of slum life. But this is that.