The lirpa is a traditional Vulcan weapon with a curved blade at one end and a heavy cudgel at the other, used in the ritual combat of the koon-ut-kal-if-fee.
The lirpa dates from Vulcan's violent ancient past and survived into modern times through ceremony. In 2267 Spock's betrothed T'Pring invoked the right of challenge during his pon farr, choosing Captain Kirk as her champion, and the two were forced to fight first with lirpas.
The weapon combines a cutting edge with a bludgeoning weight, and the fight was only ended when McCoy faked Kirk's death. The ritual later reappeared in other Vulcan stories as a link to the traditions of the planet's past.