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 called the Hammer. Mario received the Hammer after he beat the Hammer Bros. blocking the exit of Mushroom Way (In fact, the weapon has their insignia on it.). The mighty plumber used this weapon to pound enemies, at least until he found the Noknok Shell. When equipped, the weapon adds 10 attack points to Mario’s attack rating.

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, two Hammers are given to Baby Mario and Baby Luigi by the L33t Hamm3r Broz. These weapons can be used to tunnel underground (a useful technique when searching for Beans) and hit switches. In battle, Baby Mario and Baby Luigi can use their hammers to attack enemies (and potentially stun them, rendering a monster inactive for a few turns).

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.