I like just about all the ones mentioned so far, so here's who I'm currently most interested in...subject to change at any time:

-Billy Corgan (Smashing Pumpkins)....totally one of a kind
-James LaBrie...what a range
-Freddie Mercury...(dito)
-Geddy Lee (Rush)...you either love him or you hate him, but you'll always recognise him
-Robben Ford...just love the sound
-Peter Gabriel...better in his genesis years but still good
-Maynard James Keenan....pure metal power :D