MiniMega Hammer

The Mini-Mega Hammer was an item in Mario Party 4. It would either shrink or enlarge the player who was hit with it, giving them the effect of a Mini Mushroom or a Mega Mushroom. The effect was randomly chosen. The player holding the hammer could not use the item on themself. It was revealed to be one of Wario's favorite items, at least in Mario Party 4.