Gh0st
Australia's finest since 1981
Not new (well the paid sequel is) but I can't recommend this game enough.
If you like to shit your pants, this is just what you need!!
I'm not one to get scared easily but I can only play this game in short bursts!
Even if I don't see Slender Man, the anticipation gets too much and I have to turn it off.
There are clones on Android and likely iOS but I suggest playing the PC versions, in the dark & with headphones on. Totally detach yourself from reality.
The first game is as I said, a free to download and play game
Slender: The Eight Pages
http://slendergame.com/
The sequel has improved graphics and storyline but you have to buy it.
Slender: The Arrival
http://www.slenderarrival.com/
So play it, then give it to a friend who thinks they're tough and nothing can scare them
