Butch Davis is a good name, but I think the truth is that he is too old (58) and may be looking for a pay bump at UNC if he indeed did actually say he is interested.
Mike Leach would bring an exciting brand of football, but he wouldn't fit. Just a gut feeling. He is a gun slinger and takes some pretty outrageous risks.
Lane Kiffin would be nice but where is the track record? Obviously the Oakland thing was a debacle, but he seems like a stretch.
Everyone needs to get over the Spurrier, Cowher and Gruden vibe. Cowher and Gruden wouldn't take a huge pay cut to come to college football. Spurrier has said he isn't interested (Maybe he is, but highly unlikely)
To me the logical choice is Chris Petersen. He's 44 years old, younger than anyone else listed here (with the exception of Kiffin). He's a proven winner and brings and exciting brand of football to the field. The only thing that could keep him from coming to Knoxville is the Washington job. Petersen is collecting $850,000 / year from Boise State right now. UT can definately offer things that Boise State can't compete with in terms of salary. Urban Meyer, unfortunately, made it work going from Utah to Florida.
Just a thought