Jimi Hendrix. I have always thought he had a cool voice and am always surpriesed that it is just guitar-guitar-guitar, when he was a really good singer too.
The chick from Heart - is that Nancy Wilson ?
The dude from Supertramp?
Marie Osmand
Pat Benitar
Robert Plant
David Lee Roth
Neil Young.
Grace Slick
There is allot more to being a "front man" that just voice alone, of course. :)