Gladius Legis
Legend
Using shield master loses its effective rather quickly once you fight monsters bigger than you. Try using shield master in a campaign like against the giants. Completely worthless feat.
You can shove up to one size larger than you. The vast majority of monsters in the MM are Large or smaller, which will get shoved down. And in the event you do fight Huge enemies, that's where an ally's Enlarge spell comes in.