There should be an option for binaural sound for users with headphones as i think it will make the game scarier.
If you don't know what binaural sound is, its basically playing sounds to your ears separately.
E.g. You can have a sound with low volume playing in your left ear and a different sound with medium volume playing in your right.
That can be used to create 3D sound effects.
Imagine this:
You are walking down the maintenance tunnels and suddenly you hear a familiar sound right behind you, before you know it Larry is chasing you and you hear the volume getting louder and louder behind your head. You see the exit and you sprint towards it. After a moment of hiding in the bathroom you hear a dreaded sound in you left ear and before you know it... Game Over flashes on your screen while you are changing your underwear.
Here is a sound i found on Wikipedia : http://upload.wikimedia.org/wikipedia/c ... lPaper.ogg Just to give you the feel of it.
Here is a breath sound I found in game files that i modified : http://penguin321.netii.net/main/apps/u ... Breath.mp3
The sound plays 3 times.
The first one in your left ear.
The second one in your right ear.
And the third one is supposed to be behind you. (This one makes the hair on my neck stand up.

Here is another example : http://www.moillusions.com/wp-content/u ... aircut.mp3
So what do you think?