Not anime but rather a cartoon. 'Monkeyheads' which was a fictional cartoon featured in an episode of Medium. It can be found on youtube if anyone is interested. The cartoon in itself isn't scary at all but in the context of that episode (a girl was seeing home invasions and killings that were actually happening in a cartoonized version in her dreams) it was a bit creepy.
They're cartoons. How scary can they be?
i forgot what it was called but there were only 12 episodes and something about kids and one was an outcast who was treated different because they said she was dead
None of them scare me, but I do like High School of the Dead and Hellsing.