The Golden Hammer is an item that serves a similar role as the Hammer in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS and Wii U, but has a completely different role in Wrecking Crew.
The Golden Hammer first appeared in this game. It only appeared in levels with three or more bombs, that you had to set off in a certain order. Doing so will allow you to use this powerful power-up for a short time.
Super Smash Bros. Brawl
The Golden Hammer reappeared after more than a decade in this fighting game. It is a special item that rarely appears in the game and does around 30% damage to anyone hit by the fighter holding the hammer and is also swings faster the regular hammer. Sometimes a fake hammer will appear, which does no damage to fighters and makes a squeaking sound whenever another fighter is struck by it.