Mike Campbell, Barry Sless, Steve Kimmock, Larry Campbell, PT, Robbie Robertson....
Peter Rowan too. He might be the most under-rated guitar player in the bluegrass world. Known more for his songwriting Rowan can tear it up on guitar and mando too.
I think some banjo guys qualify for this too. Ben Eldridge, Tony Trishka, John Hartford, J.D. Crowe, Bela Fleck.
Matt Glaser and Tim O'Brien on fiddle. Sam Bush on mando. Grisman too.
Find a version of Jerry Garcia Band doing "Lucky Old Sun" on Youtube and check out the changes Jerry plays behind the Melvin Seal's B3 solo. Another good one is Jerry doing "I Shall Be Released". Jerry knew the blues backwards and forwards.