Stetson

The Doctor wears a Stetson.

A Stetson was a hat, typically found in the western United States. The 1,103-year-old Eleventh Doctor donned a Stetson while in Utah. When Rory complimented him on it, he replied, "It's a Stetson. I wear a Stetson now. Stetsons are cool" and the Stetson is promptly shot of his head by River Song, who had appeared behind him, echoing a previous incident with a fez. (DW: The Impossible Astronaut)