Anything psycho. I saw The Exorcist. I was 16 and it scared the crap out of me. Never saw another one. I also can't read books about psychos. Lawrence Gough writes very dark murder mysteries. As do Ruth Rendell, PD James and Anne Perry. There was a time, obviously, when I could but no more. I have nightmares.
About Anne Perry: Anne Perry is an English author of historical detective fiction, best known for her Thomas Pitt and William Monk series. In 1954, at the age of fifteen, she was convicted in the murder of her friend's mother, Honora Rieper. She changed her name after serving a five-year sentence for Rieper's murder. The events formed the basis for the 1994 film Heavenly Creatures.
I think over time it becomes more difficult to shoot horrors. As for me, the only thing that can scare you now is the sudden appearance of some kind of monster or something like that. No one is afraid of the blood that holds the floor underfoot and other nonsense anymore. Horrors are often laughable.