Married to the Mob - I saw this with a group of friends in high school, a group that was on the verge of dividing in two. One camp thought the other camp was becoming too uppity. I was with the group that walked out. I don't remember it being that bad, but I do remember it was in a style, a campy style that if you didn't buy, you hated.
Natural Born Killers - I stuck through this for about 3/4 of it because I loved Oliver Stone's visual style from this era, the JFK era where he was doing a lot of double exposures and collages. I was even stomaching the ultra-violence pretty well until they got to the jail scenes. At that point, I had such a sick feeling in the pit of my stomach that I had to walk out. I felt that if I watched any more I'd be permanently damaged.
Eyes Wide Shut - I was so, so, so, so, so bored with this movie. I got to the scene between Cruise and the daughter of one of his patients. There was absolutely not a single ounce of sexual tension between the two, and then she jumped across the small table between them to make out with him. It was preposterous, completely apropos of nothing. I decided at that point it was the lamest movie I'd ever seen. I went to see Big Daddy instead. I really enjoyed Big Daddy.
The Pianist - Again, I got such a dread in the pit of my stomach that I had to leave. It upset me that badly. I rented it later and loved it from the safety of my own living room.