Here are some pretty good bets in my opinion. These bets also require that Tiger or Rory don't get hot and lap the field.
Phil at 12 to 1 is great value.
Watson at 40 to 1 is great value. While he hasn't won he has played well this year and this is a lefty's course.
Nicolas Colsaerts 100 to 1 is a great steal. I'm going to throw 5 bucks on him. I doubt he wins since it is his first time playing Master's but he is too good to get that number.
Dufner 75 to 1
Darkhorse is Scott Piercy at 350 to 1. Course fits his game and he has the ability to go really loooooow!