In no particular order, except Swanö on top:
Dan Swanö
all albums (I've heard)
Thoughts From a Stolen Soul - Extremely well arranged and composed. The song gives off a dreamlike atmosphere. This one is my current favorite, but I have yet to hear a Swanö song I don't like. Crimson II, or Uncreation could be on there too. Or Nightfall Overture, or.....ok, I'll stop.
Diabolical Masquerade
Nightwork
Haunted by Horror - The song kicks ass. It's that simple. Usually, I'm not a huge black metal fan, but Diabolical Masquerade is very close to my favorite current metal band.
Opeth
MAYH
April Ethereal - I don't listen to Opeth as much as I used to (though I think I feel an Opeth kick coming on), but MAYH is the best album I've ever heard, and I still listen to it all the time. This song's outro is one of the most emotional passages of music ever written. :Spin:
Sigur Rós
( )
Untitled 1 (Vaka) - Some find Sigur Rós boring, but I can't get enough of it. This song is truly beautiful, and the sublime crescendo at the end is truly breathtaking.
Katatonia
All Tied
Sulfur - Try as I might, I can't pick a favorite Katatonia album.
I like them all equally. Sulfur is one of their best songs of their recent sound, with great melodies all around; the lyrics are some of my favorites, as well.
Honorable Mentions (at any point these could take the place of any on the above list):
Frank Zappa
Death
In Flames
Rush
Camel
The Cure
Children of Bodom
Huzzah!