Peyton Manning would probably be one, he basically runs that offense in Indianapolis. He's the only one that comes to mind right now, Ill try and think of some others.
I agree with all Walt's picks. Rodney Harrison might be another. I really thought that Steve Young would become one too. The way you tell if a player is going to be a coach once he retires or not is if he is a "student of the game" so to speak. For example, I think everyone knew that Mike Singletary was going to become a coach once he retired.
Do you remember when Deion said that the Falcons should fire Dan Reeves and replace Reeves with him? What are the players going to learn from Deion? Speak in the third person? Dress like a pimp?
Bruce Smith is another that I thought would become a coach once he retired.