Scariest horror film mask?

Which do you think is the scariest horror film mask?

And it doesn't have to be a thriller-killer hockey style mask...you may include anything that hides a person's face and is within a scary movie. Say, like the button-eye sack mask in The Orphanage, you can include anything like that :)
Update: Some brilliant answers so far, keep them coming!

((Logan)) she always very much scared me too! Good answer :)

And oh my god....HELLO WITCHCRAFT!!! It's been absolutely ages, glad to see you and great choice too :) :)
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