A Klingon blade with a serrated edge, designed to cause severe wounds and traditionally carried by assassins, used in the attack on Worf's brother Kurn.
The kut'luch appears in the episode Sins of the Father. Worf has gone to the Klingon homeworld to answer the charge that his father Mogh betrayed the Khitomer outpost to the Romulans, with his newly discovered brother Kurn standing beside him as his second.
Kurn is lured away and ambushed by two men acting for Duras, whose own father was the real traitor. He is stabbed and left badly hurt. Doctor Crusher treats the wound and Worf recognises it as the work of a kut'luch, the ceremonial weapon of an assassin.
With Kurn unable to continue, Picard takes his place at Worf's side. The weapon is mentioned again in the Voyager episode Real Life, where the Doctor's holographic son wants one.