While we're talking about scaring yourself silly for Halloween, I want to recommend what I think may have been the most frightening movie ever made: the 1963 movie "The Haunting," starring Julie Harris, based on Shirley Jackson's "The Haunting of Hill House."
No, it's not a traditional mystery - it's a horror story, but - unlike far too many later horror films - it achieves its effect by showing you nothing. The horror is built up in your mind and your imagination. If you're not familiar wth the Jackson book, here's the opening paragraph (the last two sentences of which are repeated as the final sentences of the book as well):
"No live organism can continue for long to exist sanely under conditions of absolute reality; even larks and katydids are supposed, by some, to dream. Hill House, not sane, stood by itself against its hills, holding darkness within; it had stood so for eighty years and might stand for eighty more. Within, walls continued upright, bricks met neatly, floors were firm, and doors were sensibly shut; silence lay steadily against the wood and stone of Hill House, and whatever walked there, walked alone."
That paragraph continues to provoke chills for me when I read it - and it is read as a narration during the opening and closing of the movie as well. It was shot in black and white, directed by Robert Wise - yes, the director of "The Sound of Music" and "West Side Story," but also the film editor of Orson Welles' "Citizen Kane" and director, for producer Val Lewton, of some marvelous low-budget horror movies, including the Karloff-Lugosi "The Body Snatchers." "The Haunting" is guaranteed to scare the pants off you; the cast, including Julie Harris, Claire Bloom and Russ Tamblyn, is marvelous. It's available from Netflix as well as from Amazon - but don't miss it. Please.