Hammer

Hammers are items commonly found in many Mario games. They've been around ever since the original Donkey Kong, in which they were used to smash barrels rolled at you by Donkey Kong. They are usually thrown by the Hammer Bros. and other enemies.

In Super Mario RPG: Legend of the Seven Stars, Mario's first (and weakest) weapon is a Hammer Bros. Hammer.

In Mario & Luigi: Superstar Saga, they are crafted by the Hammerhead Bros. out of Hoohoo blocks. They are used to smash rocks in your path, defeat enemies in battle, and hit buttons and switches. They can later be upgraded to Super Hammers and, ultimately, Ultra Hammers. They can also be used to flatten Mario so he can fit into small spaces and to bury Luigi so he can travel under gates.

In Mario & Luigi: Partners in Time, they are given to Baby Mario and Baby Luigi by the L33t Hamm3r Broz. They can be used to tunnel underground and hit switches, as well as defeat enemies in battle.

In both Paper Mario's you get upgraded Hammers as you progress in the game.

Hammers are a powerful item in Super Smash Bros. and Super Smash Bros. Melee.