That really depends on my mood, but there are basically three albums it flips between.
First: Ahab's "The Call of the Wretched Sea". I'll say this most times that I'm feeling destroy-y or angry or like rocking the everloving fuck out. Especially "The Sermon," holy shit that song kicks ass.
Second: "Ágætis Byrjun" by Sigur Rós. This is an unrecognized masterpiece that should be held equal to or greater than Dark Side of the Moon, The Wall, etc (though it often is by a lot of the people who've heard it- all my friends I've introduced to this one love it more than their own mothers). I'll say this most of the time. "Svefn-g-Englar" is the single best song every written and dwarfs the entire catalogue of probably 90% of everyone else out there. Ten minutes that put almost all the rest of my music to crying shame.
Third: "Von," ibid. To me, this is the underrated and unrecognized masterpiece, even among Sigur Rós fans- this is their album that's sold the least number of copies and is the least well-known, but is farther out there and more experimental than most "experimental"/"progressive" bands are. And it's just absolutely beautiful, especially "Hun Jorð".