Unlike anything else on this list the demon Pazuzu, as featured in several micro-moments of William Friedkin's masterpiece 'The Exorcist', was never really meant to be seen, only subconsciously absorbed in order to add yet more menace to an already nerve-shattering motion picture. When it was revealed that Friedkin had slipped in a few frames of what can only be described as an unbearably terrifying visage into his film interest grew and the pause button came into play. The simple yet horrifying image of the staring, white-faced creature is something you can only gaze upon for so long, such is its innate aesthetic evil. Nasty work.