[Marack]

Man, I have to agree with Garila. Les Claypool is probably the best guitarist ever. He trancends traditional musical thought far further than any of the others mentioned here.

Just listen to some Primus. He plays rhythm guitar, bass lines, lead parts, all while singing. Strap a drum on his back that he can opperate with his feet and he doesn't even need any other musicians. He's got easily the most inovative approach to the Large String 6 (frettless rainbow bass, ) ever. I challenge you to find any musician that can pull off what Claypool can.

As for traditional 6 string players though, I'll throw in a vote for Frank Zappa. So much good music from him its hard to decide where to start, but if you've heard enough of it you probably don't need my convincing =).