'Vapor Trails'
This one was a real grower. First time I listened to it, my response was something along the lines of "This sucks". Took about three or four listens before I suddenly realized that I actually liked the album, and from then to this day I really can't get enough of it.
It seems to exist in its own little world, not really sounding like any of the other Rush albums, and not really sounding like anything else by anyone else. The damn thing is an abrasive, chaotic masterpiece.