Having never been killed or killed someone 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.
So, to introduce this new feature to the hallowed halls of Final Girl, I give you the eeeevil Dr. Crews (Terry Kiser) from Friday the 13th Part VII: The New Blood. After meeting the business end of Jason's mighty yard trimmer:
This is what we get:
Dr. Crews, I knew you were a jerk when you used Tina's mother as a human shield...and sad to say, it's therefore fitting that you die looking so stupid.