My somewhat-conservative pick is New Mexico. Lobos are a 3 seed, yet have all the makings and I think they got a pretty good draw. To me, they're in the weakest region by far.
Still think St. Louis could make a run as a 4, but I doubt they get past the Elite 8. Michigan State is always an obvious and choice. I still think Florida could do some damage as a 3 as well. All of the 3's are dangerous to me.
Wichita State is a team I don't think anyone wants to play, including Gonzaga. I think they'll give Pitt trouble, and they could stir things up with the Zags as well.