While not the best singer, a personal favorite of mine was Lux Interior, the front man for The Cramps. He didn't have a great voice, certainly not in the same category as many of the names already mentioned but I don't think I've seen a showman more perfectly tuned to his particular audience.
For those not familiar with The Cramps, played a mix of 50's rock 'n roll with a liberal dosing of late night TV and B-movie horror schtick. They're most famous concert was in 1978 when on a west coast tour the stopped and gave a free show for the patients at the Napa State Mental Hospital.
I saw them at The Fillmore in San Francisco on Halloween night when I was in college, it was a surreal experience, there was even a patron dressed up like the old man off the cover of Led Zeppelin IV, complete with bundle of sticks. It was as if the ghost of rock 'n roll was haunting the Fillmore that night, you'd just catch glimpses of him in the balcony alcoves out of the corner of your eye.
For two hours that night Lux held court, always one to let the freak flag fly he had that crowd in the palm of his hand.
