This Dr. Horrible's Sing-A-Long Blog foto contains
boater, leghorn, panama, panamahut, seemann, skimmer, hut stroh, bootsfahrer, bein, strohhut, livorno, panama-hut, filzhut, homburg, stetson, trilby, fedora, stetson trilby, snap randhut, schnappen sie randhut, and snap krempe hut.
There might also be
kavalier hut, schlapphut, slouch hut, and kavalier hut schlapphut.