I'm sure as fine connoisseurs of horror you've all experienced this phenomena at one time or another: the Ridiculous Death Face. It occurs when the actor or actress portraying the hapless victim pulls...well, a mighty ridiculous face when they're being shown what for by the film's psycho.
Having never killed nor been killed in real life, I have no idea if people actually make faces like this when they're dying. Frankly, I don't want to know because that's a little morbid. Having never acted in a horror film, I don't know if the director tells these actors to...uh, emote this way or not. But when watching a movie, whether a good or bad one, whether I'm sucked into the action or not, these silly faces bring everything to a screeching halt, if only for a minute.