Recently someone mentioned i check out the indie first person horror title slender, based on, of course, the slenderman/tallman mythology.
Slender [Video Game] download can be found at the slender fan site.
I was actually quite impressed with this simple but scary project; defining the gameplay, it's essentially free roaming in a forest environment, you find notes in different places; apparently from people who saw the slenderman, then freaked the fuck out upon seeing this well dressed fella and did some batshit scribbles, as you would.
Be prepared if you decide to play this game at night when all of a sudden the fucking slenderman appears directly behind you even though you swore there was nothing there and you end up spilling cherry coke all over your jeans.
i wouldn't go as far as say it is eerie to the core, you do get the feeling of being followed throughout, but it's not overly creepy. it balences scares and the dread of the slenderman quite well.
Now my two cents, and by cents i mean nitpicks:
Games such as Silent Hill, Call of Cthulhu, Eternal Darkness and Amnesia really set the bar for what should go into a horror game, and what shouldn't.
When you collect notes in slender, an ambiant sound/music que cuts in, and although this gives you a perfectly executed 'wtfomfgwhat'sgoingon??' factor, it keeps playing way past making the point.
Silence in horror games is golden.
My only other grumble is that the more you see of something, the less scary it becomes; and when you're staring right at the slenderman for the first time, it's surprising, however i somewhat expected him to disappear, leaving me successfully paranoid.
They added an effect that distorts your perception as you stare, which i consider to be a vital role in horror, but it's not reached it's potential to be an effective scare, it just needs improving.
Slender is a game anyone who's a fan of horror should try, way better than most out there.
Now if you've played it and need more slenderman fix, good news, Etereal Entertainment [Manio31] is making a Source mod for Slender.
Verdict? it looks awesome.