I'm not a big fan of most of Leviathans material outside of the split with Crebain, the split with xasthur, and Tenth Sublevel.
Tenth Sublevel was an extremely atmospheric and dark journey. How can one ignore the evil genius in tracks such as Sardoniscorn and The Idiot Sun? Edit: And the title track... 15 minutes of pure fucking EVIL.
Xasthur, I really don't get into all that much, outside the split with leviathan. I try, but it just doesn't work for me.
Edit: I wanna change my vote!