Difficult to pick just one, and to put one at the top of a list would be impossible. I would say the best guitartis in no order are...
Stevie Ray Vaughn
Jimi Hendrix
Eric Clapton
Jimmy Page
B.B. King
Joe Walsh
John Lennon on "I'm Losing You" on Double Fantasy. There are some intriguing groans and moans. Considering it is from John, I like it a lot, too bad that he was probably thinking of Yoko. Not someone who would make me think of orgasms.