Did we miss Karen Carpenter?
Some think Brad Delp from Boston had a great voice. I tend to agree.
David Clayton Thomas of Blood Sweat and Tears was pretty good too!
To add to the 'Bluesy & Unique' theme:Rather some of the pretty voices on here, I prefer bluesy, unique voices. Such as this one. Noah Hunt. Kenny Wayne Shepherd Band, but Noah does most of the singing. (and then you get Kenny's guitar work)