The DING DONG is basically a tactical sledgehammer. Originally Intended for use as a breaching tool, battering ram, and pry bar rolled into one, I am guessing you'll mostly be using it for cracking heads open. Great damage & knockdown, but relatively slow on the swing.
The Ding Dong Breaching Tool is a melee weapon in PAYDAY 2 that was introduced through the Gage Assault Pack. It becomes available to all players who have reached level 48.
The Ding Dong Breaching Tool is a slow and very low-damaging melee weapon with extremely high knockdown chance - even more than the Telescopic Baton and the Baseball Bat, making it useful for dominating enemies.
The Ding Dong Breaching Tool is named and designed after the Gerber tool of the same name. This makes it the third Gerber melee weapon included in the game, the first being the Berger Combat Knife and the Survival Tomahawk being the second.
The achievement "Hammertime" is a reference to the M.C Hammer song of the same name.
There is an Overkill logo engraved onto the Breaching Tool, near the hammer end.
"Ding dong" is the most common sound of a doorbell ringing, so in a way the Ding Dong's name is a reference to its purpose: opening (breaching in this case) doors.
Despite its stated purpose, as mentioned above, the tool is not actually capable of breaking down any doors in the game.