Knives

A Knife is a small single bladed tool used for cutting things with. A knife has come to be seen as a eating tool, but it can be used for many things. Because of their size, they are easily concealed and can be used as weapons for fighting with.

One Piece
Sanji has been seen using knives for cooking as well as calling them a chef's soul. Buggy carries many knives with him, including hidden within the soles of his shoes. Other pirates and people carry knives for combat or other purposes.