Bill's Hat is a promotional cosmetic item for all classes. It is a slightly worn team-colored beret, with the yellow shield insignia (or "flash"), of the U.S. Army's 1st Special Forces Group. It is styled after the hat worn by the eponymous William "Bill" Overbeck in Left 4 Dead.
- Bill's Hat has its own intricate backstory: "While conducting a science experiment on parallel dimensions, Bill's Hat fell off a table into the Team Fortress universe."
- The beret flash on the hat is that of the 1st Special Forces Group which is based out of Joint Base Lewis-McChord near Valve's headquarters in Bellevue, Washington.