Mantine is the obvious one, having the highest Sp Def of all non-Uber Flying types. However, it also has a x4 weakness to Electric and below average HP.
If you will allow it, Togetic with Eviolite is a good wall.
Noctowl in my experience has made a suprisingly good. Wall. It has a solid HP and Sp Def stat and plenty of moves to use that help keep it alive.
Vespiquen has the move Defense Order and Heal Order, which would make it a good wall if not for its awful typing.