I've always liked the following slide players:
(Sorry, more than 10, couldn't narrow it any further. Some posters didn't include 10, so it averages out, right?)
Ry Cooder - great album: Meeting by the River (with Indian slide guitar player Vishwa Mohan Bhatt, another great)
I think most/all of the above have been mentioned, including tunings. BUT, I can't believe that since this thread originated in '07, nobody has yet mentioned one of my all-time favorites:
Mississippi Fred McDowell! (Pretty sure he uses open G (video below), not sure if he played or recorded with other tunings.
Probably a "simpler" style than many of the other players mentioned, but his music just speaks to me (talkin' direct line to the soul!). Even more than most/all of those same "more technical/proficient" players. Just goes to show...
GREAT video of Fred playing "Goin' Down To The River" here: http://www.youtube.com/watch?v=9TyzAAwJnIw
If you like slide guitar and your not familiar with Fred, or even if you are familiar but haven't seen this video - you owe yourself to take the 3 minutes to watch!
-M W Guthrie