Creepy 2D platform games

Do you know any this type of 2D platformers with a tense atmosphere, if not counting modifications of existing games like sonic.exe?
The only game I know was the PC game Abuse which I played in the early 00's. The keyboard + mouse -controls made the player immerse more to the game with its small FOV. The gameplay gave me a feeling of being followed, particularly added by the ambient howls and screams. Some of the Ant attacks were loud which made me actually jump at couple moments. Also, I played the game on dark contrast settings without music, making a malformed and nightmarish atmosphere.

Then someone may think Limbo but the game ended up being a predictable series of trial-and-error deaths and the only unsettling part was the secret dark cave where I was expecting a random jumpscare. I did like the grim, rainy city theme and the music.

Also, what about the nightmare fuel in non-scary platformers?
As a kid, I found the various giant gargoyles in Hocus Pocus rather intimidating, especially the ones in levels 3 and 4 of episode 1. While I knew their purpose as warning signs of incoming enemies, I imagined they would reanimate or damage the player if I looked them for too long.

Try All of Our Friends are Dead. It's a fairly atmospheric and creepy platformer, though it is a little short. I can't recommend the sequel, sadly, since it went more for a gothic styling and tried way too hard.

As far as nightmare fuel in non-scary platformers goes, I'd say that the Donkey Kong Country games on the SNES definitely had some pretty eerie moments. The Misty Mine levels in the first game being one prime example.

Check out this game:

http://tig.wikia.com/wiki/Eversion

It's really good and has some creepy shit in it too.

When you say Sonic.exe, do you mean the creepypasta fan game or the actual modification of the original game's rom?

I think Slenderman qualifies, considering is almost 2.5 dimensions and easily accessible to the plebeian Steam user.

Gyossait was the first that came to mind.

1213 by Ben "Yahtzee" Croshaw. Here's some info and download http://www.fullyramblomatic.com/1213/

I always found Prince of Persia to be kind of creepy.

Megalyth said:

Gyossait was the first that came to mind.

Made by the same guy who did AoOFaD? Pretty cool! I didn't realize that he'd made a third game.

B.O.B. for Sega Genesis had a creepy moment here and there.

Been meaning to play Closure; looks creepy and has a cool gameplay concept.

Oddworld exists within my childhood nightmares. I honestly don't remember it well enough to know if it would creep out and adult though.

Heart of Darkness is a rather gruesome game, especially when it comes to deaths.

This was kind of a weird game.
http://www.kongregate.com/games/TerryCavanagh/dont-look-back