"This large iron sledgehammer was originally used for mining, but it works reasonably well as a weapon too."
The Iron Sledgehammer is a weapon found in Breath of the Wild. Link can use it as a weapon to attack enemies, and also use it to build up kinetic energy in a boulder, when the boulder is suspended in time with the Stasis Rune.
These weapons are occasionally found lying around out in the open. There is one found on the Great Plateau, within the Owa Daim Shrine. While not often, they are occasionally wielded as weapons by enemies, including Black Moblin.
With a power of 12, they serve as a decent two-handed weapon during the early game. Due to its heavy weight, it is rather slow to swing, leaving Link vulnerable to an attack while he is using the sledgehammer. They are outclassed by much more powerful two-handed weapons that Link acquires. However, with a durability of 40, the Iron Sledgehammer can withstand some damage, and thus it is a great weapon to be used with Stasis.
Hyrule Compendium entry of the Iron Sledgehammer.