Cabin in the Woods
This film explored the common tropes of horror films. People often paused this scene so they could read the whiteboard to predict what else the cabin of horrors had in store. If you look closely, you can see all of the character's names and various classic horror movie themes.
Indiana Jones: Raiders of the Lost Ark
Viewers couldn't get enough of this scene when the villain, Belloq, delivers a speech while a fly slowly crawls into his mouth. The actor really did eat this fly and he did it all without breaking character.