Black Sabbath has been in heavy rotation for me since I was kid. I'm mainly in the Ozzy years camp and pretty much only listen to those albums, though I can't knock Ronnie James Dio. He did a great job coming in but overall it's their early stuff that blew my mind years ago and still does today. It's nearly impossible for me to pick a favorite album but Master of Reality is definitely at the top of my list. One of the greatest bands ever for my money who's influence can still be heard clearly.