re: Who is the biggest celebrity fan of each SEC school?

I think for Tennessee I would say Charlie Daniels as opposed to Chesney.

For Auburn, if you want to go with people who are not former athletes, I would throw in Alan Jackson and either Big Boi or Andre 3000 from Outkast (I forget which one).

Maybe Tim Cook, but he doesn't show his fandom very often.

Although not a celebrity, Auburn also had a fan in the White House - Obama's first press secretary grew up in Auburn. Even though he went to NC State he was very vocal in his support for Auburn during the 2010 season.