12's in most shoes. And I definitely do not envy anybody with feet larger than mine, for two reasons. One, I have to walk down stairs sideways because it's too awkward to walk down with my feet facing forward. And two, I know (from working in a shoe store) that 13's are usually not even stocked, and sometimes 12's as well. I always felt really bad for the guys who would come in looking for something larger than 12.
Plus I grew into 12's around the beginning of middle school. Thank God my feet stopped growing, it was getting a little ridiculous to have size 12 shoes at age 12...