What is everyone's favorite video game soundtrack?

Hotline Miami, Shenmue 1-2, Shatter, Shadow of the Colossus, Chrono Trigger, Super Meat Boy, FTL, Half Life 2, Witcher, Blood Dragon, Mass effect series, Risk of Rain, Akira Yamaoka's works etc... but there's more I'm probably forgetting some at the moment

Hotline Miami, Electronic Super Joy, FTL, AC4

Ys Seven!

http://youtu.be/uGW0fYvs_m8

Journey, XtremeG Racing Association, Final Fantasy saga, Panzer Dragoon, Castlevania Symphony of the Night, Shadow of the Collosus and ICO.
And many more...

Surprised that no one mentioned Omikron: The nomad soul. For the people who like the Hotline Miami soundtrack it might be worth it to check out Nidhogg's soundtrack, appearantly Daedelus contributed to it!

Hotline Miami, Rayman Origins, Rayman 3, Morrowind, Beyond Good Evil, Mass Effect, Burnout Paradise

Painkiller, Return to castle Wolfenstein, Red Alert 2, these are the games with the most awesome soundtracks I could come up with, top of my head.

Battlefield 1942

Mafia II, with no doubt

Duke Nukem games, Shadow warrior classic and 2013, Serious sam games, Resident evil ( 1-4 including rebirth, then it was meh ), Dead Rising games ( dunno about 3rd but 1 and 2's ost is awesome ), Aliens Vs Predator games ( really cool ), Max Payne games, Skyrim and much more that i forgot ... Lots of good OSTs XD

Ōkami: Never even played the game. A web article made me listen to this and then instant love it.
Trine 2: Pretty much all of it.
Halo series: Some tracks from Reach (Ghosts and Glass, Ashes) and most of the first half of ODST track.
Skyrim (LPO arrangement)
Alan Wake
Chrono Trigger
Castle Crashers
Rayman Legends: Most of the game, really, great song.
Crysis 2 (Hans Zimmer's track only)
Gears of War 3
Puppeteer: Also never played the game, only watch walkthrough cuz I don't have PS3

Clicky

A Walk in the Dark, BeatBuddy, and Botanicula

Bust a Groove 2

Jet Set Radio Future

Hotline Miami

Right here.

Portal 2's OST is AAAAaaaaaAAAASOME!!!!.

Also, FTL, Trine 2, Bastion, Hotline, Metro 2033, TF2 and Killing Floor

Starbound

TimeSplitters 2 had some pretty kickass music. http://graemenorgate.bandcamp.com/album/timesplitters-2-ost

And Then There Were None:

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Megaman series but MM2 and MMX are all-time faves, Castlevania series but specifically Castlevania 2: Simon's Quest for fave, Legend of Zelda series, Crystalis (NES not Game Boy Color version), Wanderers from Ys III, Skies of Arcadia Legends, Beyond Good & Evil; Blocks that Matter, Botanicula, VVVVVV, Aquaria, Driftmoon, La-Mulana; An Untitled Story, Treasure Adventure Game (free, remade into the pay game Treasure Adventure World).

First one that popped into my head was the Sword and Sworcery OST, which I listen to pretty regularly. VVVVVV and Bastion have awesome music too.

Everything from Kingdom Hearts series!

Metal Gear Rising: Revengeance and pretty much every else Metal Gear series game too.

And of course To The Moon!

The one that goes dun dun dun doo doo lalala dungdigido dun dun dun ziz zimmie zoo.

Resident Evil 2, Killing floor, Brutal Legend, Every single Painkiller OST, Deus Ex Human Revolution, Devil May Cry 3 and DmC, Silent Hill Origins (but all the ost of the series are cool), Gears of Wars

heroes 3, still.