A Waluigi Launcher is a weapon used by Wario, Mario, and SuperMarioGlitchy4 in several bloopers. It appears to be a Waluigi held horizontally. This launcher debuted in The Wacky Wario Bros.: Wario's Treasure Hunting Time, where Wario used Waluigi as a projectile as defense from Donkey Kong.
According to The SMG4 QNA (400k Subs :D), a Waluigi Launcher can be made in just a few steps. After finding a Waluigi, his internal bone structure is relocated, an explosive is inserted between his buttocks, and the Waluigi is ready to be fired or thrown. Waluigi usually screams a lot when launched.