Prince. Dammit, beat me too it. But he is an excellent musician, a virtuoso.
Jeff Beck - Probably the least celebrated of all the 60s guitar players
Grateful Dead - Behind all the mistique, these guys were good songwriters. Sometimes the drugs got in the way of the band, but Weir, Lesh and Jerry knew how to play.
Velvet Underground - Bob Dylan meets the MC5.
King Crimson - The one prog band with both chops and a rocking edge.
Talking Heads - Byrne is cool
Sun Ra - The most underrated yet influenicial, and perhaps contraversial jazz man ever.
Frank Zappa - Style and a sense of humor
And of course Phish, who IMO are a wonderful blend of all the above bands.