Nuttin' but blues!
I love most of the guys mentioned here...Buddy Guy, Taj Mahal, SRV, Gary Moore, Robert Cray, Muddy Waters, Albert King...
A band (which many wouldn't consider hard core blues) that I love crankin' in the car stereo is Blues Traveler. All their CD's are well recorded and that lead singer can really tear it up on the harmonica.
I used to like that blind guy...Jeff Healy...but he seem to disappeared after only a couple of CD's. I love the guitar playing of Robben Ford but he's a terrible blues singer unfortunetely. Hiram Bullock and Larry Carlton have got some mean blues licks as well.