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Nightmare Fuel: Shaun of the Dead
Spoilers below. Oh, and you've got red on you.
Near the end of the film, David is dragged through a window by zombies kicking and screaming, and is gruesomely disemboweled, torn limb from limb, and eaten alive. Ouch.
Early in the movie, Ed and Shaun are driving down a road, and you briefly see a family trying to get away from their zombie mother, who drags the son back inside the house.
The lights being switched on in the basement of the Winchester. We're expecting, when Shaun goes into a dark room alone, that he'll be attacked by a stray zombie trapped in there. We don't expect that when he switches on the lights there are dozens and dozens of gore-smeared zombies pawing at the window in complete silence.His knee-jerk reaction of turning off the lights and pulling down the shade somehow makes it worse, because now they're out of sight but definitelynot out of mind.
The revealing of Pete's zombification. At the beginning of the film, as Shaun is getting ready to go to work, he snaps shut the mirrored cabined on the bathroom wall to reveal the reflection of an irritated-looking Pete moaning about the door being left open overnight. The next day, as Shaun is steeling himself in the bathroom, he snaps the cabinet shut again — but instead of a perfectly-alive-if-not-somewhat-pissed-off Pete reflected behind him, there's the dark, silent shadow of a man standing perfectly still on the other side of the shower curtain.
It's worse when you remember Ed's unintentional prediction from the night before... "The next time I see him (Pete), he's dead!"
Some of the unnamed zombies wandering around outside the Winchester are utterly terrifying if looked at closely. A special mention goes out to the identical twin zombies; identical twins can sometimes be unsettling in their own right, but the blood-stained, blank-eyed bodies of two fairly large and completely indistinguishable men lurching around just sends shivers down your spine. Furthermore, when the group pass them in their bid to reach the Winchester, a garbled scare chord plays, which only exacerbates things.
The events around Shaun's mum. There's the bit where you see her arm with a gaping hole in it, Shaun having to rush away from zombies invading their safehouse to watch his mum die, convulsing as she does. The off-screen shotgun-cocking sound just afterwards, with one of his "friends" pointing a shotgun (rightly, but tactlessly) at her. And then being handed a gun and told to shoot your own mother, and the effect when her face changes just before he does.
The part where Mary falls down onto the umbrella stand, complete with blood splatter. And then she manages to lever herself up off the stand, with much snapping and squelching, and as she stands up we're shown the lovely hole going right through her body. Uuuuuugh.