Puking, Surgery Scenes (Like has been said), and any time when somebody ingests something that was not meant to be ingested.

When I was young, I was watching some movie that, to this day, I undoubtedly did not understand at all. Whatever was really happening, it seemed to me, small, stupid, hyperactive child who wouldn't go to bed and wanted to watch freaky movies in the wee morning hours like I was, what was happening seemed to be that a woman was walking in the park with a man.
OMFG!!!!!!111oneone11!
Well, there's more to it than that. Ya see, she pulls out this tiny mallet. And I think she, like dipped it into his neck. He choked to death on the thing.
Really wierd. Most bizarre thing I've ever seen. I changed the channel and there was a classroom filled with bloody elementary school students, all face down in their desks.

Most horrible night of my life. I'm reminded of it whenever something unnatural is inserted into somebodies body. Like a hammer. *Shudders. And then again.*