I'd say Metallica's Ride the lightning or Judas Priests Painkiller for single best heavy metal album. But Paranoid is a great album indeed. I can't get enough of songs like Electric funeral, Fairies wear boots and Hands of doom.
A lot of people cite that album, but I have to say that Master Of Reality is far superior in my opinion... Far darker and mysterious, and with far heavier, monolithic riffage..
Garage inc? *pukes* you deserve to be banned for saying that i gotta say Piece of mind by maiden, priest's painkiller, tallica's kill em all, or sth like that
Deep Purple's Machine Head is first on my list, just ahead of paranoid. These two were practically ISSUED to new metalheads for over two decades!
/me agrees with Raddish-licious. However... is this thread about *heavy* metal only or also about other subgenres? Because I know tons of perfect albums but all of them are other styles of metal (mostly black, unsurprisingly). You think so? Hm, I like Call of ktulu much more...