Five of my personal favourite horror films, in no particular order:
Dead of Night, Ok so it bumps the list up to six but so what. Just room for one more inside, sir...
The Hitcher, A truely epileptical slasher. In fact I'm not sure I should be calling it a slasher movie at all. It's too out there for it.
The Invisible Man, A cheeky sci-fi horror with fx work that still holRAB up 70 years later.
Night of the Demon, Absolutley. Bloody. Terrifying.
The Shining, So many theories and so little time. That's why it endures. Oh yeah and "I'd sell my soul... just for a glass of beer. Hi Lloyd. Slow night tonight, huh?"
The Thing, John Carpenter's BEST horror movie and the best 'effects' horror flick ever although The Fly is a close second.
Also ran: An American Werewolf in London, The Bride Of Frankenstein, Cat People (1943), Dawn of the Dead (1978), Don't Look Now, The Exorcist, Freaks, A Nightmare on Elm Street, The Texas Chainsaw Massacre (1974), The Wicker Man.
Actually it's just so hard to choose...