I have two scenes I can't watch: First, in the Disney version of The Hunchback of Notre Dame, there's the scene where Quasimodo is tortured by the crowd. During that scene, I always have to look away or close my eyes; I just can't watch it. The poor guy is being tortured all because he doesn't look like a supermodel!

Second, there's a scene in the movie version of Of Mice and Men: *spoiler-ish, though nothing TOO major* The scene where Curly starts provoking Lenny and Lenny fights back by crushing Curly's hand was bad enough in the book, but it was just horrifying to watch in the movie. You really feel for Lenny when Curly starts lashing out at him (mostly due in part to John Malkovich's outstanding performance), and then when he starts fighting back by crushing Curly's hand, there's the sound of the bones breaking, plus his knuckles start to bleed...ugh.
Basically, it's hard for me to watch scenes where a character is being tortured, which is why I couldn't read Blubber; Judy Blume is one of my favourite authors and I love her books (especially her Fudge series), but one quick skim through Blubber and I knew I'd never be able to make it through, having been a former victim of bullying.
(I know the topic is about movie scenes, not books, but still, you get the idea)