A bokken (木剣, boku = wood, ken = sword) or bokuto (木刀) is a wooden sword used primarily for practicing sword arts. Leonardo utilized one in his earlier years, and again in his old age, where he wielded a custom carbon one created by Donatello that ran on bio-electricity generated by his life force.
Splinter uses this weapon in the 2012 TV series' episode "Baxter's Gambit" to train the Turtles into perceive incoming unseen attacks.