Description: Resembling to human eyes something like a small metal profile of a bat in flight, the kailune is a throwing blade which Romulans once used to hunt for food or sport. It is sharp on all edges, the better to increase the chance of inflicting a wound on a target.

Although it it generally not powerful enough to kill an adult Romulan, some masters have demonstrated a lethal pinpoint accuracy with it. On rare occasions a kailune's ability to kill will be increased by coating it with poison.

Source:

Star Trek TNG RPG - The Way of D'era - The Romulan Star Empire (page 65)
thedemonapostle