It is a unique auto axe that deals much more damage than the original. It has a larger damage/hit and damage/second ratio compared to the standard auto axe (45 compared to 35) and uses less AP (50 compared to 65).
The Mauler can successfully strike about 356 times from full condition before breaking.
Auto axeThe Pitt (add-on): A modified and stronger version of the steel saw made out of old car parts
Man OpenerThe Pitt (add-on): A less strong variant that ignores armor(power armor included).
Steel sawThe Pitt (add-on): A weaker version of the auto-axe that can be found on certain slaves.
Though The Mauler is the single most damaging melee weapon (with the exception of the Shishkebab with the Pyromaniac perk), it is also the heaviest, making it a more difficult weapon to carry around.
As this weapon hits exceptionally fast for a melee weapon, using the perks Superior Defender and Ghoul Ecology can lead The Mauler to a much greater DPS stat.
Grinding barrels and other physics objects will usually result in damage, as they will be pulled violently into the player, then spat off in some random direction at a decent rate of speed proportional to the mass of the object; Cars will sometimes scoot towards you, barrels will hit a player hard enough to damage, and shopping carts rocket off like bats out of hell. It is possible to kill non-player characters with lots of patience and no repercussions, by repeatedly flinging barrels at them with The Mauler.
Behind the scenes
The fact that Everett mentions Monroeville, PA and chopping up ghouls with it is likely a reference to the fact that the Monroeville Mall was the location where the original Dawn of the Dead was filmed and in Night of the Living Dead the police and news casters call the zombies "ghouls". Also, "zombies" is a common derogatory name for ghouls.
ps3pc When using it in FPS mode it may disappear mid-animation, bringing up the Pip-Boy immediately afterwards you will notice that your Pip-Boy has disappeared too (but not the screen). Changing to a different weapon quickly clears this bug.