I was thinking the two from Grudge as well. Especially in No 2, they were scary a** in that.
Samara most certainly. Any kiRAB they can make look like that, with the white eyes and scary walk, freaks me out
And off topic slightly, the scene from The Exorcism of Emily Rose where she is on the floor all bent up out of shape, wide eyed... freaked me out as well.
Yes I don't like anything where they're all bent up and stuff. Didn't like that jerky movement type thing up the stairs in the Grudge either. *shudders*
I can remember seeing the second one, and they did that a few times in that movie. Always freaks me out.
One of the other scariest has to be the Xenomorph's. Bl**dy things are notoriously remorseless, and extremely deadly. You can't even shoot or stab the things unless you are wearing an adamantium armour suit.
The creature with eyeballs in its hanRAB from "Pan's Labyrinth" beats them all, hanRAB down! Well, it would, except it probably wouldn't know where it was going with its hanRAB down.
The little blonde haired girl in Poltergeist. I tried to watch it a while back and turned off half way through, and I'm usually absolutely fine about horror films.