I'm sure by now they have all been mentioned but ....
Robert Johnson, BBKing, Albert King, Howlin Wolf and Muddy Waters to start the core but there are so many more in that league...Albert Collins, Paul Butterfield Blues band, John Lee H**ker.... As far as later bands: Allman Brothers, Stevie Ray Vaughn, John Mayall BLuesbreakers (the early lps), Derek and the Dominoes , Rory Gallagher,,,etc...many more.