I'll second all of those recs (although I'm not a fan of At The Gates or Amorphis, and I haven't listened to half of the black metal or doom metal bands).
Also for the Doom list, add Bongripper and Pillars
edit: and for the Death list, add Drawn and Quartered because they are seriously one of the best death metal bands ever
Originally Posted by Fat Deschain
add Asphyx to this too. The whole death/doom genre is something I've been trying to get into lately but I'm backlogged into 2012 right now