Tekkō-kagi

Tekkō-kagi, (手かぎ手虎 lit. "back of the hand hooks"), were a kind of kakushi buki (隠し武器; lit. "hidden weapon") deployed by the ninja of Japan.

Weapons of these type are presumably easier to conceal and use in close quarters, depending on the size and nature of the blades. However, in fights involving larger weapons they would be less effective considering their limited reach compared to a sword or polearm.

Weapons of these type were actually used in early civilizations. The Bagh Nakh, or Tiger's Claw, was originally developed in India for self-defense and used by the first Maratha Emperor Shivaji. Ninjas would used the Nekode/Shuko for fighting, and the Tekagi-Shuko for utilitarian purposes, such as climbing trees.

Trivia

 * In the 2012 series, in the episode "Rise of the Turtles, Part 2, all four Turtles are seen using smaller versions of these, (known simply as "Shuko"), to scale the wall of the Kraang compound. When Donatello palm-slaps his own forehead at Michelangelo lack of grasp of Leonardo's plan to distract the Kraang, he forgets that he's wearing a pair of Shuko and hurts himself.
 * In the 2012 series, in Splinter's flashbacks, The Shredder is seen weilding a pair of "Tekagi-shuko/Tekko-kagi", (lit. Tiger hook hands"). In the present, he is seen with custom-made Tekko-kagi claw weapons: They have extendable blades and are razor sharp. They have also been shown to be strong enough to cut through metal shipping containers.
 * In the Marvel Comics franchise, the Tekagi-shuko are the inspiration for the retractable claws of one the franchise's leading characters, Wolverine/Logan.