I'm going to say Bob Dylan. Some can't get into his music because of his voice (Personally I love his music. His 1965-67 material is brilliant, brilliant, brilliant. But I digress...) but so many musicians and artists have tried hard to ape his iconoclastic coolness for so many years and none have succeeded. People like David Bowie and Lou Reed come close, I guess, and I really like their music for the most part, but where Dylan seem so real, so profound, they come off as a bit superficial by comparison. Not only did Dylan do the "rebellious" thing with pointing out the evils of adult society, he pointed out all the problems with his own generation and never took his "followers" and "idolizers" seriously.
This is really hard to judge, now that I think about it. "Coolness" is even more subjective than "artistic merit" or the ever so arabiguous "it's good music" explanation for liking a style.