Other possible lost gems -- from reliable sources, but sometimes my taste/discernment is based on a different matrix of selection:
This band isn't bad. Kind of like a doomier Autopsy at parts, at other times like a hardcore punk band, this falls within the same realm as Impetigo or Sadistik Exekution in its sprinkling of various metal genres throughout its sound. Kind of hokey, though.
Pretty cool early punk band. Not on the same level as Black Flag, Misfits, or The Stooges, but still enjoyable for the style.
TOTAL FUCKING DESTRUCTION
Side project of Rich Hoak, drummer of Brutal Truth. 3 words - Really. Freaking. Annoying.
Dutch hardcore punk band. Like Siege and Cryptic Slaughter, an early example of the genre morphing into grindcore. Incredibly fast and energetic, but can turn incoherent and repetitive. I enjoy them, but casual grind/hardcore/"powerviolence" fans should avoid.
Along with Rorschach, Human Remains, Neuraxis, Burnt By The Sun, and a few select others, this band is one of the few metalcore bands worth spending any time on. Though composition is simple, primitive even; there is spirit and drive behind the early material. I cannot comment on later material (past the 3rd album) as I've not heard it. Can remind of neanderthalish-type hardcore kids, but those moments are few and far between.
LAST DAYS OF HUMANITY
Probably the extension of extremity within the grindcore genre. They were fantastic live. As for their studio work, the last two albums they produced can barely be called grindcore, as the music is simply a mess of blasting, gurgling, and fuzzy guitar/bass work. The earlier material is in the Carcass/Exhumed/Hemdale vein. For what it is, pretty good all around. Casual grind fans would probably not enjoy this.
Simple, punchy, vibrant early UK punk. Catchy, great for working out to.
BLUE OYSTER CULT
As far as rock music goes, they're in the top 10% of quality. "Agents of Fortune" and "Tyranny and Mutation" each contain about half an album's worth of creative, evocative "space" rock, with progressive and heavy metal influences. They have a penchant for writing a few duds, with halfformed ideas that make little sense. I wouldn't bother with most of the 1980s material.
Hope this helps out some people.