Boomstick

The Boomstick is a gun found in Jungle Shrines. The Boomstick fires a spread of three shots, but only consumes one bullet to do so. All three shots have a base power of 12, yielding 19 damage with Musket Balls and 21 damage per shot with either Meteor Shot or Silver Bullets. Highly effective at close range, hitting an enemy with all three shots can do around 60 damage, butchering most non-hardmode enemies. Due to the spread of the shots and the slow weapon speed, the Boomstick loses efficiency at long range.

Trivia
Due to its location in the Underground Jungle, this weapon is probably a reference to the game Spelunky, which features a very similar shotgun. This weapon's name may also be a reference to the film Evil Dead 3: Army of Darkness. Ash Williams: "All right, you primitive screw-heads, listen up! See this? This... is my boomstick!"