If it's blues slide you like, the late Duane Allman was one of the best, Warren Haynes [Government Mule] is also very good. You can also go back to the roots where a lot of contemporary sounds came from - e.g., Muddy Waters, Howlin' Wolf, Hound Dog Taylor, ... If you want to go way back, try Elmore James or the grand daddy of them all- Robert Johnson. Hey, old EC ain't to shabby either.