Hatebreeder
Pizzicato Heartstrings
For me it's a tie between Hvis and Filosofem, which are the only Burzum albums I own so far. I'd get more, but I can't find any at decent prices.
I found the Burzum/Aske album and Det Some Engang Var today at the music store for less than $10 each. I'm in ecstasy.