Who's the best blues harp player.

My votes would include those already listed above, and I'd add the following fine harp players to the list:
1. Carey Bell
2. Sonny Boy Williamson (I and II)
3. Slim Harpo
4. Kim Wilson (from Antone's in Austin, TX)
5. Paul deLay
6. William Clarke
7. Jerry Portnoy
8. Howlin' Wolf
9. Junior Wells
10. Jimmy Reed

Alot of really good ones have already been mentioned but Mark Wenner of the Nighthawks should be on the list as well. He's got one of those killer gravelly voices to boot.

Although I am a huge Junior Wells fan (Junior was a superb vocalist as well), I'd have to give the nod overall/all around to Little Walter with respect to playing. Sugar Blue is also a superb modern day player; technically there are not many who can hold a candle to him but I think he finds it difficult to fit his ego into most rooms.

honorable mention-corky seigel,paul jones(ex manfred mann),the late great paul butterfield,the late great keith relf.

-Walter Horton (on the album: "Johnny Winter"),
-Whomever played on "Must Have Done Somebody Wrong" Allmans/Filmore East
-Whomever plays for the 'Stones (Jagger?) particularly "Midnight Rambler"
-Whomever plays for Zepplin (Zep-II, "Bring it on Home")

Sorry I'm such an ignorant music lover...