A neural truncheon was a device used by the Breen that delivered a painful jolt of energy into a person's body to incapacitate them.
In 2375, Worf was controlled by the Breen personnel of the Tykk by being repeatedly jolted with a neural truncheon. (DS9 episodes: "'Til Death Do Us Part", "Strange Bedfellows")
In 2382, Sarina Douglas was tortured by a Breen with a neural truncheon. Douglas was late able to subdue her captor with his own neural truncheon. (ST - Typhon Pact novel: Zero Sum Game)