The super sledgehammer is the best melee weapon in terms of damage and knock-back effects. However, the greatest drawback of using it is that it knocks opponents very far away, giving fewer opportunities to strike in a single round. Though often rare, they also are the most valuable close combat weapon in the game.
In Navarro, located on the ground floor of the facility in the maintenance building east of the hangar, in the right-most of the two workbenches behind Quincy. He will not take kindly to anyone going through his stuff so he has to be distracted or snuck past.
Used by a bounty hunter in a random encounter upon being a Childkiller, having killed at least two children and being between levels 7 and 12.
The last super sledge may also be found in the armory of the Enclave oil rig.