Description: Kill 25 enemies with the Paddywhacker hand cannon.
Gamerscore: 5g
A good place to farm this is after you open the tear to the alternate Columbia ("Open the Tear" is the quest), which is part of The Good Time Club chapter. Load that chapter, fight through the club, then progress through the chapter until you get to the jail in the basement.

Once you've done that (you'll be in the room where you found Chin, dead), go back up the stairs of the jail. Once back upstairs where the cells are, there is a hand cannon in the first room on the left with 27 rounds (where Slade is, if you saved him previously and didn't come across him going through here previously). Go back the way you initially came through the projector room, and when you get to the stage, you'll get ambushed by about six or seven enemies. It will take two shots each unless you headshot them. Once they're all dead and Elizabeth talks to you again, reload the checkpoint and do it again - takes just a few minutes each reload.

On your way back to the stage and upstairs, you will come across a room with a cabinet of carbines, if you choose to farm those here as well (there is a lockpick in this room).