Las: hardcore came from 'hardcore punk' whichi isn't the same as hardcore, or punk. It's silly, but people like to overclassify. Depends on who you ask on what is hardcore and what is not. I tend to call 'hardcore punk' bands hardcore, like old Husker Du, Minutemen, early DRI, UK Subs, Crumbsuckers etc because I'm too ashamed to admit that the current wave of retarded slayer-meets-madball type of bands exist, much less deserve their own genre.
My personal metal favourites include early progressive metal/involved thrash metal like Coroner, Psychotic Waltz, Mekong Delta, Deathrow, Midas Touch, Watchtower, Sieges Even, Megace to doom metal like Candlemass, Shape of Despair, Skepticism, Evoken to some extremely idiosyncratic and unclassifiable bands like Maudlin of the Well, The 3rd and the Mortal, Unholy