Who's your favourite rock vocalist.

Moe_Zambeek

Bon Scott and Alex Harvey

Rod Stewart in his early days.

Royston Langdon from Spacehog.

Mike Farris from Screamin’ cheetah wheelies /
solo.

Brian Johnson before he blew his throat out. 

Mark Lanegan in the last years of Screaming Trees and a few years after.

Terry Reid on superlungs.

Ian Thornley, especially when he holds it back a bit.

Svennn

Current favourites

Lars Sarfsund
Kent Hilli
Dino Jelusik
Eric Martensson
Andre Linman
Andy Kuntz

and must add to the other greats already mentioned 

Brad Delp
Sean Harris
Glenn Hughes

Kebabkid

Freddie Mercury
Brad Delp
Richie Kotzen
Steve Overland (FM)
Bobby Kimball of Toto (back in the day)
Brian Johnson

On the softer side, Steve Perry & Deen Castronovo (drummer) of Journey - listen to the latter singing 'Mother Father' or 'Separate Ways'. He sounds like the former

Cols

Already mentioned, but absolutely worth mentioning again:

Freddie Mercury 
Paul Rogers
Chris Cornell
Robert Plant

However, I can’t believe we’re three pages in and no-one has yet mentioned Jack Bruce.

hollywoodrox

Jagger ,Steven Tyler & Axl  although Axl’s a bit off par of late 
  Special mentions to Jizzy Pearl Kip Winger and Gary Cherone 

gretschthumper

Steve Marriott could belt a song out like no other
Rod Stewart in The Faces - Stay With Me is a good example
Paul Rodgers in Free and Bad Company was pretty astonishing

munckee

Slightly left field choice but I’m having a real REM period again lately and I’ve always thought part of the quality of their sound was Mike Mills backing vocals.  

Deadman

PJ Harvey

SidNewton

Deadman said:

PJ Harvey

Great shout. Been listening to a lot of her over the last couple of months. Top class.

MrTee

Deadman said:

PJ Harvey

'Long snake moan' makes this soooooo true

Edit: amongst many others, obviously 

Grumpyrocker

Ozzy 
Ian Gillan
Ronnie James Dio
Bruce Dickinson
Tom Englund (Evergray)
Nick Holmes (Paradise Lost)
Tony "The Cat" Martin
Floor Jansen
Robert Plant
Alyssa White-Gluz (Arch Enemy)
Heike Langhans (Draconian, Remina, Light Field Reverie)
Jonas Renkse (Katatonia)
Mikael Akerfeldt (Opeth)
Mariusz Duda (Riverside)
Amy Lee

Just a few favourites off the top of my increasingly forgetful head. But my all time favourite Rock/Metal vocalist is Anneke Van Giersbergen.

Hoof

Chris Cornell
Iggy Pop
Neil Fallon
Troy Sanders 
Matt Caughthran (The Bronx)

markj

Sammy Hagar.

StefB

Three pages in and no-one has mentioned the great David Coverdale. Untouchable in his prime. 

Sammy Hagar 
Bob Catley 
Bruce Dickinson 
Steve Overland
John Payne
Paul Rodgers 

Vintage65

All the usual suspects have been mentioned already, so I'll just chuck Greg Dulli into the mix...

CE1

Patti Smith
Kurt Cobain
John Lydon
Paul Di’anno
Eddie Vedder
Bob Mould
Ian Astbury
Joe Talbot

Strangely I really cannot get on with Chris Cornell, something about his voice I just don’t like.

TTBZ

Pretty much all the grunge legends apart from Vedder.
Frank Carter
Neil Fallon

Corey Taylor

Howard Jones

guitars4you

Paul Rogers

Not really rock but Don Henley by a country mile is one of the finest vocalists out there

DaveJames

George Fornby

rsvmark

Chris Cornell
Freddie
Ronnie James Dio

thats it. Plenty of other excellent leads but faves? These 3