Originally Posted by -GP-
Can't help you with horror anime, but if you'll settle for horror manga, you could do a lot worse than Uzumaki.
Only 3 volumes and all sorts of twisted stuff.
Well, when it comes to Horror Manga, there is a better selection.
The manga version of "The Ring" is more of a mystery manga until the end, but it has a decent suspense build.
Nightmares for Sale is a "series of random stories" manga, where it all revolves around one particular mysterious shop. The stories range from tragic, gruesome endings, to ones of happiness, depending on how the main character of the particular story reacts.
Higurashi: When They Cry is another Mystery Horror manga set in a small Japanese village they may be cursed. I only read one chapter of this manga. But it definitely raised some questions, and the creepy factor was up there.