What are the best horror anime series'/films?

I really am not a big fan of Halloween. Don't get me wrong, I love candy just as much as the next person. Now that I'm an adult, I can have candy whenever I want! That right there killed off a lot of my interest in Halloween. When you can pick up candy and not have to dress up for it, things certainly change.

With that said, I am a fan of horror features. Be it traditional movies or TV shows, anime or literature, I do like to get scared. The issue is, I never really do get horrified by this stuff. A lot of the content that Hollywood pumps out is nothing more than cheesy or gory. I can appreciate that stuff and laugh at it as well, but it's not going to make me jump out of my beard.

I was looking to turn to you guys to find out some of the scariest anime features out there. I know there's a handful of horror-related anime to pick up, whether it focuses on monsters, ghosts or what have you. Sadly, my knowledge in this area of anime is a bit lacking.

What is the scariest anime you've ever seen? Is there a horror anime that really makes you shiver every time you think about it? It's okay if it's a gore-fest anime as well. All is fair when you're in the month of October!