I'm riding 23 Gatorskins. Since the heavy tires come thicker, I dropped down to 23. Though I used to ride Fortezza's in 23 which were amazing. Damn Chicago debris...

On a related note - how many people use mismatched tires - something like an Armadillo or Gatorskin on the back for toughness and a lighter tire up front? I've never quite flatted a front tire.