This Neil Patrick Harris photo contains
boater, leghorn, panama, panama hat, sailor, skimmer, straw hat, snap brim hat, fedora, felt hat, homburg, stetson, and trilby.
There might also be
dress hat, high hat, opera hat, silk hat, stovepipe, top hat, topper, beaver, pith hat, pith helmet, sun helmet, topee, topi, cavalier hat, and slouch hat.