Kogatana

This traditional samurai dagger, (like a Tanto but smaller), is often used as a secondary weapon to a Katana, and is great for close range combat and surprise attacks.

The Kogatana is a small, slim, short dagger used by the Turtles. The ones used by the Turtles are light, straight, and perfect for throwing.

According to the Concept Art of Leonardo's Katana, "Niten Ryu", in the 2012 series, a "Kogatana" (Mini Katana) is concealed within the Saya's (Scabbard's) binding wrappings, and a Tanto blade is concealed within the hilt of the "Daito" (Long Sword), all as secondary, auxiliary weapons to his Katanas.