MarbleHornets

this shit scared the living hell out of me D=
i'm not even sure if it's fake or not anymore (you have to watch all 27)

https://www.youtube.com/watch?v=Bn59FJ4HrmU

this is just a link to the first vid

Um......ok
i just see a guy just standing there, how is that scary? :T

again, you have to watch all of them.
also, it would help if you read about the myth of that guy.

http://marblehornets.wikidot.com/slender-man

the scariest ones are the last two, and somewhere around entry 19 it gets really fucking creepy.
admittedly, i didn't think they were scary at all when i first started watching them. but as it progressed, i assure you, i was on edge 90% of the time.

also, make sure you pay close attention to the details of the surroundings in the videos.
paying attention to the fire escape behind the guy's head in entry #7 will give you an idea of what i'm talking about.