"War fans could also be used as weapons. The art of fighting with war fans is tessenjutsu."
Tessen were folding fans with outer spokes made of heavy plates of iron which were designed to look like normal, harmless folding fans or solid clubs shaped to look like a closed fan. Samurai could take these to places where swords or other overt weapons were not allowed, and some swordsmanship schools included training in the use of the tessen as a weapon. The tessen was also used for fending off arrows and darts, as a throwing weapon, and as an aid in swimming.
Makes this seem a little more badass: