This One Direction photo contains
fedora, felt hat, homburg, stetson, trilby, boater, leghorn, panama, panama hat, sailor, skimmer, straw hat, and business suit.
There might also be
porkpie, porkpie hat, dress hat, high hat, opera hat, silk hat, stovepipe, top hat, topper, beaver, pith hat, pith helmet, sun helmet, topee, and topi.