Long-time viewer who registered just for this post chiming in with A few favorites. Apologies for Youtube, but that's where I listen to most of my music.
First off, the Menu theme from HAWKEN:
HAWKEN is an online multiplayer game where you stomp around in mechs and shoot other people stomping around in mechs. It was fun enough for a little while, but this song was the only thing from it that really stuck with me.
FUCK, I love this music. That bass synth, those drums, that plaintive refrain... This music makes me want to strap into a war machine and go to town with some brothers-in-arms. The fact that it played during the menus was a nice touch; as you prepared your mech's loadout and waited for the next match to pop, the music made it feel like you were really gearing up for war.
The rest of the soundtrack was forgettable (quite literally: I can't remember if there even WAS any more music than this), but this one track will stick with me forever, and has earned a permanent spot on my PvP Youtube playlist.
Second, "Chant" from Dawn of War:
Dawn of War is an RTS set in the grim darkness of the 41st Millenium. Gameplay-wise it's mostly same-old RTS stuff, but two things set it apart: it's portrayal of 40k's setting, and a soundtrack by Jeremy Soule.
I have a soft spot for music with a lot of gravitas. Chants, choirs, strings, haunting chords, just give me all of that forever. I also am in absolute love with the Warhammer 40k universe, so this track obviously stands out for me since it relates to both. It kind of summarizes the feeling I look for in that kind of music: Brooding and minimalistic. Just listening to this, I can imagine myself sitting in the cloisters of a Fortress-Monastary as the Chapter prepares for evening services.
Next we have the theme from Bit.Trip Runner 2:
If you like good music and rhythm games, PLAY BIT.TRIP RUNNER 2: FUTURE LEGEND OF RHYTHM ALIEN. If the name alone doesn't pique your interest, then at least try it for the music.
I am incapable of feeling sad when I listen to this game's soundtrack. It's just so energetic and peppy. The soundtrack as a whole is amazing, but the theme is especially memorable, and you'll hear its leitmotif woven into most of the other tracks. The music really made that game, and I've spent hours struggling through difficult levels on it just so I could hear more.
Next on the list, Our Perception of Beauty (aka Drusera's Theme) from Wildstar:
Wildstar was, at best, a forgettable MMO that predictably languished into F2P Limbo, but it did have a few thing going for it. It was humorous, had some very interesting environments and characters, and it had an amazing soundtrack.
Composed by Jeff Kurtenacker, the music in this game was wildly varied in tone and orchestration, and did a lot to add to the character of the areas you explore and the people you meet. This track in particular stands out to me for the sheer, raw emotion in its theme, and it can still bring a tear to my eye.
And we'll end with an obscure one - The main theme from The Void:
The Void is an incredibly unique game (and would make excellent material for a Game Dungeon episode, wink wink) with an equally unique soundtrack. Strange, oppressive synth tones, tribal beats, high, wailing harmonies... this game's music is likely not everyone's cup of tea, but it leaves an impression, regardless. And it only serves to add to the sensations of curiosity, confusion, dread and wonder as you explore the game's environments and meet its characters.
I could likely spend forever listing favorite tracks for games, so i'll leave you with five. Happy Birthday, Ross, and hope you enjoy!