Sunn O))) - Black One
This is a favorite of mine mostly because of the amalgamation of drone and black metal. You can see this in almost all the tracks, either through the "riffing" or just because of the presence of Wrest or Malefic. Although Wrest only makes one appearance on this album (It Took the Night to Believe), it's worth listening to. He really gives it his all, and it sounds like it could have been released under the Leviathan name. Malefic makes many more appearances, not just on vocals, but also on guitar and keys. His best track (arguably) on this is Bathory Erzsebet, where the band went so far as to lock him in a casket to record vocals (Malefic is claustrophobic). This one track lacks the vocal distortion that is typical for his vocals which really changes things. Instead of the haunting style that is typical of Malefic, you can truly get the feeling that he's scared. It's so wonderful. The other tracks are "standard" Sunn tracks, full of prolonged chords and feedback. However, each has something special that makes it slightly different than a normal Sunn song, whether it be the vocals, slight drumming, or just a different style, and it truly makes this album more of an experimental effort than anything. There's also an Immortal cover (if you can call it that) in here that's worth checking out.
Cursed Realms (Of the Winterdemons), Cry for the Weeper, Bathory Erzsebet