Capt. Picard, Obi-Wan Kenobi, Brom (from Eragon, the book, not the shitty movie), Durzo Blint (Night Angel trilogy) Garrus, Wrex, Tali, or Joker (Mass Effect 1-2) Professor Xavier, Ezio Auditore, Gandalf, Allonon (Shannara series), Giles (Buffy The Vampire Slayer), the list goes on. A school with these guys as teacher would be badass. but to choose one... damn that's hard.