I skimmed through the older pages of the forum and didn't find this as a topic yet, so please forgive the redundancy if it's already been brought up.
I'm thinking not just of bands/projects that have a great deal of filth and distortion with their recordings, but those that use their instruments to create actual noisescapes. Either is acceptable.
I suppose Abruptum would be the something like the originators of this sub-genre. There could well be BM groups leaning more towards pure noise than structured songs before them, but I haven't heard of them. I tend to think that Venom's use of pretty blatant noise, such as tracks like "Aaargh!" and Cronos's live bass solos, could be said to have paved the way from music towards something more blatant.
Stalaggh also should rate a mention - leaving aside rabbiting on about their "vocalists", they do come up with some pleasant sounding material. The layering of their recordings by Xai-Das on the "Projekt Terror" dvd sound pretty satisfying to me.
Please list more (I imagine our own Ryan Wreck will have something to add, at least).