Yeah

I can think of a couple off the top of my head:

Freddie Mercury
James Hetfield
That bloke out of Rammstein (although that's mainly because I don't know anyone else who sings in German!).

Evan Dando
Tom Petty
Steven Tyler

Jason Perry
Bruce Dickinson
Justin Hawkins
Marilyn Manson
Damon Albarn
Mark Greaney (JJ72)

And there's loads more too...

Axl Rose too

Off the top of my head:

Tarja Turunen [Nightwish]
Vibeke Stene [Tristania]
James Dean Bradfield [Manic Street Preachers]
Axel Rose [Guns 'n' Roses]
Ozzy Osbourne
MeatLoaf
Skin [Skunk Anansie]

Couple more from me..

Ian Watkins
Billie Jo Armstrong
Dave McPherson!!
Matt Heafy (When he's busting out a growler of a vocal)

Imogen Heap (though not necessarily if the song was 'Hide And Seek')

Kate Bush
Polly Jean Harvey
Sinead O'Connor
Matt Johnson (The The)

Loads more, and Dido too

Rob Thomas (Matchbox Twenty)
Jon Bon Jovi
Adam Levine (Maroon 5)
Wes Scantlin (Puddle of Mudd)

Apart from the ones already mentioned i thought of:

Tim Armstrong (Rancid)
Brody Dalle (Distillers)
Davey Havok (AFI)

I also thought Jello Biafra from Dead Kennedy's was fairly distinguishable but could just be me. Dexter Holland from Offspring, but that could be just cos i'm so used to it.

Oh and also Justin Pierre from Motion City Soundtrack