The scene where Rose Byrne sees the man standing by the baby's cradle and when the guy walking outside suddenly appears inside the bedroom in Insidious. Also when Darth Maul sticks his tongue out beside Patrick Wilson when his mom's talking about her dream.
The scene in The Exorcism of Emily Rose when her boyfriend wakes up and sees her staring at him while lying on the floor all contorted and the one where the priest spots the devil in prison.
The scene in The Ring when they show the face of the dead girl in the closet.
The scene in The Fourth Kind when Milla J's character gets abducted.
The scene in The Others when Nicole Kidman sees the old woman instead of her daughter.
The last scene of Paranormal Activity and when the demon slams the kitchen in PA 2.
The creature in Rec/Quarantine.