OK, metal has no representation here, and this is what I've been listening to. It's definitely not your typical stuff, and isn't quite well known.

Electric Wizard - Return Trip: http://www.youtube.com/watch?v=fXpFV9sW2bI

Electric Wizard is the essence of Doom with guitars so down-tuned, the strings hang off the guitar and can be used to fire arrows.

High On Fire - Devilution: http://www.youtube.com/watch?v=euALIidJYsA

High On Fire is the complete package with intense vocals, driving rhythms, and overall listenability. More 'casual' listeners will find this approachable rather than the expected onslaught of guitars and screaming that usually comes with the territory.

Uncle Acid and the Deadbeats - I'll Cut You Down: http://www.youtube.com/watch?v=kSpsffboOAc

Moving back to the 60's, this is more like rock today, but the dark edge and disturbing vocals make it more the choice of the metal fan than any 60s metal listener.

Elder - Hexe: http://www.youtube.com/watch?v=Y48mDuY8rI0

A symphony of darkness. This song is lengthy, like a journey into some hopeless and dark abyss. Listen to it.

This is stuff I wrote my Master's Dissertation to, in addition to baroque classical. Sometimes you need a little darkness and to behold the apathy of the universe to trudge forward.