Slingshot

A slingshot, also called a shanghai or a catapult (not to be confused with either the catapult siege engine or shepherd's sling) is a small hand-powered projectile weapon. It has a pocket for holding the projectile. Each end of the pocket is attached to a rubber band, which is attached to the ends of a fork-shaped frame.

Usopp's main weapon is a slingshot. In addition, in the 4Kids dub, some guns were replaced with slingshots.