I suppose I telegraphed this yesterday, but I have just two words to begin: Black. Sabbath.
I know that most fans believe that sabbath ceased to exist for all intents and purposes when they kicked Ozzy out in 1979. Ronnie James Dio will always have a special place in my own musical heart, however, because he is (a) short; (b) has one of the more distinctive voices in heavy metal; (c) and so earnest, taking himself and his goofy lyrics so seriously. Also, I think that "Heaven and Hell" is one of the best Sabbath songs ever, right up there with "Paranoid" and "N.I.B."
Lest you think I have taken leave of my senses completely, I think much of Ozzy's later solo material, with Zach Wylde on guitar, is far superior even to the music of early Sabbath. My own favorite is "No More Tears".