Waluigi's stick is an object that Waluigi found in Wario and Waluigi's Super Adventures Ep. 2-5: The Search For The Star and kept for the rest of that season. He used it to attack Shadow in Ep. 2-5, and in Ep. 2-6, Wario used it to trip King Dedede. Finally, in Ep. 2-8, he defeated Meta Knight using it. It is possible the stick has some sort of magical power since it has been used to defeat so many people, despite being an ordinary branch..
The stick was also mentioned in "Mario Goes to Court" when Wario pays Waluigi a piece of grass for being his lawyer. Waluigi says, "Ooh!! I can add this to my collection with my stick!" This marks the only time the stick was included in a video outside of the Wario and Waluigi's Super Adventures series, though a similar stick was used to free Waluigi from a sock in "Wario's Secret Club".