Michael Bloomfield is without doubt my favorite electric guitar player. He was just so expressive...
Among currently active players I like Ronnie Earl alot, and of course the great BB King.
Beyond that, I hesitate to single anyone out, because I just love the whole style. I tend to especially like whatever I'm listening to at the time. All the electric stuff from Chicago in the 50's & 60's is terrific. Junior Wells was one of my first "favorites".
Stevie Ray was a breath of fresh air in the 80's. Seeing him when he first came to the Northeastern US blew me away.
For acoustic blues, some guys are special to me. Skip James, Blind Lemon, Willie McTell, Bukka White...
I'm sure I'm forgetting some HUGE ones, but if I don't stop I'll list every notable blues artist I've ever heard. If anyone is just getting into the blues, this stuff on this thread is highly recommended.
-Chris