Just as learning is an important function of the hero, teaching or training is a key function of the Mentor. Training sergeants, drill instructors, professors, trail bosses, parents, grandparents, crusty old boxing coaches, and all those who teach a hero the ropes, are manifesting this archetype.
Of course, the teaching can go both ways. Anyone who has taught knows that you can learn as much from your student(s) as they do from you.
Who have been some of your favorite teachers, Mentors, and/or hero turned Mentor?