In my opinion Ronnie James Dio (Black Sabbath, Rainbow) is the best metal singer ever! If you have heard Heaven & Hell by Sabbath you will know what i mean. Ialso really like Bruce "Air Raid Siren" Dickinson (Iron Maiden). If you have heard either of these two you will note that high range and lots of vibrato is what i like in vocals :p. However, Hetfield, Mercury and Guilmour are good too. Did Waters really sing Hey You? I could swear Dave sang all Floyd songs...