For today's offering it's Regan from 'The Exorcist'. Again, super late with this one, but what can you really say about this movie? It's been a long time since I've seen it, but the way the movie slowly builds up the whole possession business, ratcheting up the tension and the creepy atmosphere is excellent. People focus so much on the shocking moments that they forget how the film gets to work at unsettling you right from the very first scene.
I can't remember exactly who, but I'm sure I've met at least a couple of people who claim this film never scared them the first time they saw it, generally this is backed up some stupid claim, like they were 9 years old at the time or that they actually found it quite funny. Another thing I've heard people say is something like "I'm not religious, so no film based around demons or the devil really scares me". It's probably due in part to the reputation it has as "scariest film of all time".
Here's the thing: if you say that 'The Exorcist' did not scare you, or at least unsettle you, then you are a fucking liar.