This Bruno Mars foto contains
fedora, vilten hoed, homburg, cowboyhoed, trilby, fedora met vilten hoed, and stetson.
There might also be
porkpie, porkpie hat, porkpie hoed, vierdeukenhoed, campagne hoed, schipper, leghorn, panama, hoed, zeeman, skimmer, strooien hoed, livorno, panama hoed, matroos, and stro hoed.