The Sledgehammer is available to the player in Apocalypse Weekend after fending off the zombies from the Greasy Panda restaurant. A man who appears to be a high-ranking soldier approaches Postal Dude and tells him that he "likes his style" and gives him the job of killing diseased cows at the Cow Pasture. To kill the cows, the man gives Postal Dude the sledgehammer and some grenades. The sledgehammer, when used, will completely decimate the victim's head, killing them instantly. The secondary attack will make Postal Dude throw the sledgehammer in the direction he is facing, and like the main attack, it will decimate the head of the first person in its way. After which, the sledgehammer must be picked up again. However, when playing in Enhanced Mode, a thrown sledgehammer will not be removed from the inventory and may be thrown over and over in quick succession like the machete. The sledgehammer is capable of ricocheting off walls if the angle it's thrown in is correct. The sledgehammer can destroy doors, same as the axe and the chainsaw. However, the sledgehammer destroys doors in one hit.
The weapon is very effective against zombies as any of the two attacks destroy their heads, killing them. Generally, the sledghammer is very effective against anyone and anything. The only enemies which are immune to both of the sledgehammer's attacks are certain bandits (those that wear motorcycle helmets) in Paradise Lost and the National Guard soldiers, as their ballistic helmets absorb the hits but also stuns them in the process. The player might get a few seconds during which the soldier recovers from the attack to use another weapon and finish the soldier, or flee. However, unlike the National Guard, bandits wearing helmets will not get stunned, but can still be killed by the sledgehammer.
If the sledgehammer is thrown at a cow's butt, the handle will be inserted into the animal's anus. The Postal Dude then says phrases like "Oh man, how I will get that back". The cow will remain paralyzed until he recovers the hammer by simply touching it.
Postal III Edit
The Sledgehammer returns in Postal III. It's primary attack is an overhead strike. It's alternate attack is a strange spinning attack allowing the dude to his multiple enemies around him. It shares its movements with the fire axe.