After some of the shit I've seen, I guess I've become highly desensitized or something. Most of the recommendations on here don't really register anymore.
Outside of the obligatory Ichi the Killer (sort of), Oldboy (probably), Requiem for a Dream (for sure/definitely), and Salo (haven't seen yet, but will in a few days, and I hear it is definitely difficult to watch), this thread mostly sucks honestly.
Props to the people who said Inside and Irreversible. Those definitely belong. Honestly, you could probably put/pick any film out of the New Wave of French Horror of the past/current generation and add it to the list. For me, I was going to say Inside, my most recent film that made me feel uncomfortable, but to keep the list fresh and add something new, I will just say Martyrs. That is one
ed up film, especially the latter 1/3-2/3 of the film where it strips away any semblance of plot or story and transforms wholly into a torture film/porn epic. Some of the most disgusting shit I've ever seen.
Also, I enjoyed the film overall, but I guess to a certain degree, Teeth, left me disturbed. I guess it's just the whole girl with a ravenous vagina that bothered me.
Also, I haven't seen it yet, but the word on the street is that A Serbian Film is highly graphic/gory/extreme/etc. and is the new bar to see how well you can stomach film.