Kirk Hammet of Metallica?
Possibly ,but DEFINITELY in my opinion, Dimebag Darrel of Pantera, he IS heavy metal and has been for the past like 15+ years.
Ritchie Blackmore, Angus Young, Johnny Ramone.
Did Tony Iommi ever sing?
Ah yes, Malmsteen. A no-talent hack if ever there was one. 
He actually did sing lead on a cover of Hendrix’s “Manic Depression” (and if I never hear him sing again, I’ll be a happy man!)
Steve Howe never sang lead with Yes, I think he might have sung on his solo albums though.
Eddie VH & Tony Iommi never sang lead, either (to answer the people that posted in the form of a question.) I don’t think Iommi even did backing vocals, whereas Eddie certainly did.
Maurice Deebank from Felt.
Didn’t Slash sing on some crappy solo album?
Anyways, the only singing Lifeson ever did for Rush was carefully edited out by producer Geddy Lee (the Show of Hands concert video).
BUT: he did some of the vocals on his solo project Victor, so he doesn’t qualify.
Brian May certainly does sing and has several solo albums out.
In the parallel ‘immortal guitar’ thread which old Coldfire closed, I’d just asked about the ‘she’ part of notcynical’s OP.
Any female guitarist I can think of also sings. The closest I can come to in terms of guitarmanship is Tina Weymouth of Talking Heads, but she sings her stuff with Chris Frantz (her husband, also of Talking Heads) on Tom Tom Club records.
What female guitarist fits the OP?
Jimmy bloody Page
Ritchie sodding Blackmore
enough already.
How about Charlie Christian and Wes Montgomery?
Joey Santiago of der Pixies
Sorry for dragging up an old thread but Chet Atkins sang quite often, especially on his later albums. Of course he put out so many albums it’s not surprising everything didn’t turn up sooner or later. It was probably only a lucky chance that we didn’t hear him play the sousaphone.
Nothing fancy, just simple stuff – kind of accompaniment to his guitar when needed. And a lot of times when he’d accompany another artist they’d do vocal duets, too. Knopfler, Dolly Parton, Suzy Boguss, Doc Watson and even Les Paul – another mentioned here as non-singing. The best vocal number he ever did, IMHO, was “I Still Can’t Say Goodbye”, a tribute to his dad.
And although he certainly is rightfully recognized for his guitar virtuosity he was first hired in Nashville as a vocalist!!