Well, since you opened it up to any scary movie, here are some of the scariest I know. And I am not cheating and going to a website for this list but giving you actual movies that I saw, so keep that in mind.
Alien, Carrie, The Ring, Ju-On (this was remade into The Grudge, which was also scary, but the orignial is scarier), The DEvil's Backbone, Jeepers Creepers, Silent Hill, Brahm Stoker's Dracula, The Omen (the original version is very scary), The Lost Boys (Ok, so not very scarym, but it IS about vampires -- and it's good), American Haunting, Scream (only the first one), At Dawn they Sleep, Salem's Lot (vamps), Interview with a Vampire, Once Bitten (actually a comedy starring Jim Carrey, but still, about vampires so is Buffy the Vampire Slayer, the Movie), Sleepwalkers, From Dusk Till Dawn, Bordello of Blood, Blade, Blade II, Blade:Trinity, Queen of the Damned, Nightmare on Elm Street, Halloween, Mothman Prophecies, The Village, Seven, Texas Chainsaw Massacre (again, the original was scary), The Dawn of the Dead remake scared the hell out of me, so did 28 Days Later, Poltergeist, Jacob's Ladder, Rosemary's Baby, Amityville Horror, The Sixth Sense, Arachnophobia, Psycho, The Shining, Pet Sematary (almost any Stephen King movie). My friends thought the Blair Witch Project was scary, but I thought it was boring. Almost any Wes Craven movie too. He made one called Vampires that was pretty good.
These are in no particular order, by the way. Hope this helps. have a spooky Halloween!