Anything off E.S. Posthumus's third album, anything by Two Steps From Hell, and the Gladiator soundtrack are my standbys.
The Mod with the Migraine
There's TONS of good music on www.ocremix.org that I have used for RPG soundtracks. I actually had different lists sorted - creepy, combat, Big Bad - but I do have something like 200 songs downloaded from there.
Also, consider music from albums like the London Symphony Orchestra Best Game Music Ever, or instrumental groups like Rodrigo y Gabriela.
That’s the epitome of privilege right there, not considering armed nazis a threat to your life. - Silasw
I use OC Remix and various anime songs pretty much exclusively myself.
Kyle can attest to what songs I use in my current game after all.
The Showrunner of Dzwiedz 24
If you and your group doesn't have a strong memory of Call of Duty Modern Warfare 2 (soundtrack by Hans Zimmer), then I wholeheartedly recommend it. It has a wonderful apocalyptic, gritty, dramatic feel throughout. It's available on Spotify too.
Handy-Dandy Chord Finder
Two steps from hell, and Blind Guardian are my favourite fantasy RPG music
"I thought Djent was just a band" -Physical Stamina
Lesbarian
Perfect music for the climactic last battle somewhere down the line: Sacred Realms, by Blind Guardian.
Beyond that... I'll have more suggestions when I wake up.
Mura: -flips the bird to veterinary science with one hand and Euclidean geometry with the other-
I recently used the instrumental version of To the Beginning by Kalafina for the battle where the party fought the God of Aggression.
Official Tesladyne Employee TM
There is a lot of Homestuck music that could work well, depending on what you need it for. (Admittedly there is also a lot that would be utterly useless.)
You are dazzled by my array of very legal documents.
I'm starting a new RPG over the summer and need help coming up with a soundtrack. It's going to be an Apocalyptic Interplanar game, with the characters being the only ones who can stop the Big Bad plane destroyer from the Far Realm. I'm going to use Metallica's "For Whom the Bell Tolls" for the first session, but need help finding more music to set the mood.