Highschool of the Dead
Another
Corpse Party: Tortured Souls
Higurashi When They Cry
Parasyte: The Maxim
Elfen Lied
Monster
Vampire Hunter D
Hell Girl
Yami Shibai: Japanese Ghost Stories
Puella Magi Madoka Magica
Shadow Star
Tokyo Ghoul
Mononoke
Shiki
Pet Shop of Horrors
Paranoia Agent
Serial Experiment Lain
Blood+
Ghost Hound
Devilman
Gantz
Blue Gender
Pupa (Scary in more ways than one)
Tokyo Ghoul
Black Butler
Another
Death Note
Deadman Wonderland
Blue Exorcist (If that counts)
Parasite
Hellsing
Ajin
Corpse Party
Akame ga Kill
I can list 11 easily. All of these I watched.