Hammer Suit

From Mariopedia

This power-up appeared in Super Mario Bros. 3, where it transformed Mario into Hammer Mario, as Hammer Mario, the player can throw hammers, which can damage certain enemies (ie: Boo) which cannot normally be attacked. The hammers, unlike fireballs, fly in a parabolic arc. This makes it sometimes difficult to aim the attack, but it usually does not present much of a problem.