In Mailbag Monday #5, Angry Grandpa stated that he needed a new hammer for destroying things.
In Mailbag Monday #6, AGP recieved the hammer after a fan sent it to him. At the time, it wasnt named anything.
The Hammer was first used to finish off AGP's lawnmower after he had already destroyed it.
In "ANGRY GRANDPA DESTROYS PS4!", AGP, raging over the fact that Michael and Bridgette refused to come to his house to make Christmas Cookies with him (believing he was going to prank them), rushed out of Michael's living room only to return with the hammer in his hand, using it to destroy Michael's beloved PS4 as punishment for not coming over. He proceeded to decimate the PS4 with the hammer before destroying Mike's coffee table with it as well. At the end of the video, as AGP stands over the destruction, he picks up the crowbar and blows the dust off of it, naming it "Mr. Avenger".
At one point, AGP forgot Mr. Avenger at Michael's house, leaving without the weapon. After the PS4 destruction, Michael decided not to return the weapon to his father, and stated that he would never give it back because of what he does with it.
In "ANGRY GRANDPA'S TOYROOM MELTDOWN!!", AGP, while visiting Michael's house, found Mr. Avenger and proceeded to destroy Mike's WWE toys and wrestling ring with it, reclaiming his lost weapon.
In "THE FUTURE OF THE ANGRY GRANDPA CHANNEL", after AGP's untimely death, Michael, after discussing his plans for the AGP Show channel at the end of the video, holds Mr. Avenger in his hand up to the camera, telling his father he's doing this [continuing the AngryGrandpaShow] for him, he loves him, and that he now has Mr. Avenger. He kisses the weapon for AGP and stares at it before the video closes.