I never really got that deep into DSBM, but I have always been a fan of Xasthur through random tracks on youtube (missing out on a chance to buy Nocturnal Poisoning on cd is a regret of mine). I always liked his "2005 Demo," as it was short, dense, and had cover art that matched the music perfectly.
Another release that I always liked was Shining's Through Years of Oppression compilation. Some of the most shocking cover art that I have seen, and the Halloween theme cover that they titled "Black Industrial Misery" was amazing.
It is also worth linking the "One Man Metal" documentary series to this thread: