USC. Their offense is unstoppable, and their defense will come around by midseason. I wouldn't be surprised to see USC and Oregon both be undefeated when they meet up in November, Oregon win in LA, then USC win the rematch in Autzen in the Pac-12 title game to earn a spot in the title game. The Oregon offense is tough to prepare for, but give Monte Kiffin two looks at it in less than a month, and I think he'll be able to prep for it.
Also, I like Barkley to win the Heisman.