IMHO this Jo Cocker cover was unusual in that it created a very different, almost unrecognisable (and much improved) song. It also happened to be a fantastic performance.
[youtube]http://www.youtube.com/watch?v=mEdV-zK8UOQ&feature=related[/youtube]
I'm a big Hendrix fan but I can't get excited about Watchtower. However I think his version of Johnny B Goode at Berkeley Uni stands out as one of the most exciting exhibitions of talent ever. He does seem to become one with his instrument.
[youtube]http://www.youtube.com/watch?v=gTemxX7yNNM[/youtube]