Lately, I've been noticing more and more the aesthetic quality of a well done guitar tone in the context of a great metal album. In very rare cases (like Dead Infection's first album), the guitar tone actually makes me dislike the album. I particularly enjoy some degree of fuzz or crunch when I listen to metal. The glossy overproduced sweep-happy sound can take a long walk off a short cliff.
If forced to choose, I think "Age Of Quarrel", "The Rack", "Harmony Corruption", "Nightmare or Reality", and "Hvis Lyset Tar Oss" have my favorite guitar tones. (I know two of these are hardcore punk albums but I figure it's related)
ANUSians, what are your thoughts/favorites?