Reggie White is my favorite Vol all-time with Peyton a distant runner up. These two are head and shoulders above the rest in my book.
Way after Peyton, you then have guys who were great with good character like Eric Berry, Al Wilson, Dale Jones, Johnny Majors, Heath Shuler, John Henderson, Frank Emanuel, Paul Neumoff, Condredge Holloway, Stanley Morgan, Antone Davis, Johnny Jones, Travis Stephens, Jack Hacksaw Reynolds, and Richmond Flowers.
Then after that I would put guys who were great players but were either too cocky like Willie Gault and Carl Pickens, too difficult and moody like Arian Foster, or character flawed like Travis Henry, Reggie Cobb, Jamal Lewis, Albert Haynesworth, Dale Carter, and Tony Robinson. A lot of additional guys unmentioned fit into this third group for various reasons.