Trainspotting....
Maybe not the whole movie, but the bit with the baby crawling on the wall was bad enough for me straight I doubt that I could handle that coming down.... Another bad one would have to be "GO" only because it's such a crap movie.....
I agree with "Requiem for a dream" and "Mulholland Drive"... maybe "The Blair Witch Project" for the simple reason is that I am dizzy enough normally, extremely dizzy when coming down, so I would be massively knackered trying to watch that with all those crappy camera work.8(