Surprised nobody's posted yet, but RIP to the Prince of Darkness, Ozzy Osbourne. Those early Black Sabbath records are untouchable, and they basically invented a genre (that sprouted its own sub-genres). All the stuff that came later -- the TV show, for example -- can't reduce the impact of his and the band's contributions.
I never saw them. Had the opportunity, but wasn't into high ticket prices and stadiums. I imagine some folks here might have seen Sabbath in those early days...