I'll keep it pretty simple for now.
Some of my modern (2000 and onwards) faves include (in no particular order):
You're Next, V/H/S ("Second Honeymoon" is a particular highlight), Neon Demon, Silent Hill, 28 Days Later, The Babadook, It Follows, SAW, The Descent, The Green Inferno, Oculus, The Witch, The Sacrament, House of The Devil, Black Swan, Housebound, REPO! The Genetic Opera, A Horrible Way to Die, The Cell, Beyond The Black Rainbow, and The Lords of Salem to name a few.
Classics (pre Millennium):
Halloween, Alien, Nightmare on Elm St., Psycho, Deep Red, Opera, The Shinning, Phenomena, Cabinet of Dr. Caligari, Suspiria, Scream, Perfect Blue, Carrie, The Texas Chainsaw Massacre, Silence of the Lambs, Child's Play, Evil Dead, The Thing, The Exorcist, The Blair Witch Project among others.
Now, I know not all of these are "horror" per se, but they have frightening/disturbing elements to them that I think they each fit the bill well enough to meet the category. Plus, I'm not listening sequels or remakes for now, because it gets kinda tedious splitting hairs about good/bad qualities among them.
I would like to start a discussion about any of these thoughts, likes/dislikes OR any others you guys want to add.
