Misericorde dagger. A long thin dagger used to euthanize people who were too wounded to survive but whose wounds were not immediately fatal giving them a quick death instead of a lingering one. The name comes from the latin for 'act of mercy' and was used extensively in the Middle Ages and into the 17th century. The mercy kill was usually done by thrusting down between the neck and collarbone and piercing the heart. Another was was to thrust through visor into the eye socket and brain.
These daggers could also be used in close hand to hand combat.