I really hope it's not horror. There are about 10 good horror films ever made imo.
Off the top of my head.
Halloween, The Thing, Night of the Living Dead, Dawn of the Dead, A Nightmare on Elm Street, Trick'r'Treat, Evil Dead, The Mist, Thirst, Let The Right One I, Scream, Scream 2, Alien, The Shining, Psycho, The Exorcist
Is that more than ten?