Looking for a little spooky mood music for that haunted house or Halloween party this year? Video Games have (unsurprisingly) churned out some eerie soundtracks over the years, usually accompanying a horror title (although not always). So if you're looking to add some spooky music to that party of yours, why not start off with a quick youtube search for a few of these soundtracks (search the name of the game and OST). Once again, these are in no particular order, they're just some creepy soundtracks. A word of advice though, unless that you're a glutton for punishment, don't listen to these alone in a darkened room.
Metroid Prime 2: Echoes
Part of what makes Echoes soundtrack such a fitting choice for Halloween is the whole Dark World portion of the game. Not only do you get a soundtrack that pulls on the feelings of isolation and loneliness, but jumping into the dark world gives you a darker and creepier version of that whatever song you last listened too. Very atmospheric.
Resident Evil 4
I've listened to more of these then the Silent Hill soundtracks, so I can safely say that pretty much any one of the Resident Evil soundtracks is going to be a safe bet for finding nice and eerie music for your Halloween playlist. RE4 in particular, while not music you would normally listen under and other scenario, is definitely creepy and atmospheric on a high level. Just for fun, sneak the ending credits theme into your playlist, which starts off nice and peaceful before getting gradually darker and darker, ending with a purely unsettling chill.
Its an old classic. You're alone, armed with whatever weapons you can find, and facing nothing but hordes of demons. It's not for everyone, but it does make for great background music. If you don't dig the classic midi nostalgia however (or your guests don't) then I reccommend doing a quick search for "The Dark Side of Phobos", a more up-to-date version of the classic Doom soundtrack. Note: the video link is not the "orignal" midi material, but a more up to date version.
Left 4 Dead 1 and 2
I'm including them both on here for a specific reason. The original L4D is a bit creepier, playing more on the scary side of things and raising the creep factor. The sequel, while still having plenty of creepy music in it's own right (Zombie Clown theme anyone?) tends to put a more "boo-yah" spin on it with more kicking instrumentation. Either way, you really can't go wrong.
Metroid: Zero Mission
The original Metroid had some nice atmospheric music that, while not nearly as creepy as some of the music on this list, is still nicely ominous. Of course, Nintendo was nice enough to give us an updated form of the game with Zero Mission, with a redone soundtrack to boot. Zero Mission's music is ominous and tense without pushing you into the level of "Oh crap I'm going to die". A good soundtrack and perfect for Halloween.