This Keira Knightley photo contains
boater, leghorn, panama, panama hat, sailor, skimmer, straw hat, fedora, felt hat, homburg, stetson, trilby, porkpie, and porkpie hat.
There might also be
dress hat, high hat, opera hat, silk hat, stovepipe, top hat, topper, beaver, campaign hat, and snap brim hat.