Usually Trader O's.
(Trader Joe's version of Cheerios. You can get a whole giant box for $1.99!)
Other options:
Cheerios
Shredded Wheat
Grape Nuts
Corn, Wheat or Bran Chex
Generally, cerals that don't have any sugar or honey added (Yuck!) or aren't flakey and sog out the minute moisture hits them. Boring, I know, but one of my healthier habits.