Definitely Joel Selwood. Best player on the team, top 5 leader in the comp, amazing clubman, does so much for the community. Jibe a close second but I don't think he does enough away from the club.
AWTA, Selwood's courage, competitive spirit and desperation are a little ahead of Watson IMO. Wrote about it last night actually http://sportsreligious.wordpress.com/2013/04/22/who-is-the-afls-best-captain/