I don't go for bands as much as guitarists, and sometimes singers. So I'll just give you a list: Hendrix, Page, Iommi, Blackmore, Yngwie Malmsteen, John Christ (early Danzig), Slash, Angus and Malcolm Young, Dave Murray and Adrian Smith (Iron Maiden), Randy Rhoads, Jason Becker, Marty Friedman, Dave Mustaine, André Olbrich (Blind Guardian), Kenny Hickey (Type O Negative), Stevie Ray Vaughan, Kai Hansen (Helloween), Rolf Kasparek (Running Wild).... phew!
As for singers, except for Peter Steele (Type O Negative), I usually enjoy high-pitched metal types the best. So guys like Bruce Dickinson, Dio, Hansi Kürsch (Blind Guardian), and Michael Kiske (early Helloween).
So what about your favorite bands? Feel free to avoid the question by naming favorite musicians instead if you want to, too.