Oh God, so many folks I could name, but if I had to break it down, I probably feel these artists the most...
Albert Collins (all his Alligator stuff)
Son Seals (his first several Alligators)
Hound Dog Taylor (everything)
Koko Taylor (I GOT WHAT IT TAKES is the shit)
Little Walter (Chess Best-Ofs)
Sonny Boy Williamson (KING BISCUIT TIME kicks ass)
Lonnie Brooks (BAYOU LIGHTNING, TURN ON THE NIGHT, HOT SPOT)
Mississippi Fred McDowell (Arhoolie stuff)
Katie Webster (her Alligator CDs)
Big Bill Broonzy
Blind Willie McTell (Yazoo comps)
Magic Sam (BLACK MAGIC)
Earl King (SEXUAL TELEPATHY CD)
Slim Harpo (flawless)
James "Thunderbird" Davis (CHECK OUT TIME CD)
Muddy Waters (almost all of his Chess shit, and his Johnny Winter-produced shit, too)
There's others I've heard, but these artists come to mind most often for me personally.
PEACE!