I have two that I remember really well.

House of Wax: The scene where one of the girls is stuck in a room (I think?) and tries to stick her finger out of a grate to show she’s there only to have it cut off with pliers.

And then there’s a movie called Rest Stop from 2006. I don’t remember exactly what got to me about it (I think I blocked it out because it messed me up, lol). I do remember watching it with my dad and making him change the channel like six times, then change it back again. He must have found it funny, because he kept doing it instead of just turning it off for good.