Mafia III

The Dart Gun will become available for use during the first Bounty mission. Fortunately, pedestrians around New Bordeaux count towards this achievement, so once you have access to the gun, feel free to parade around one of the busier districts of the city, stunning anyone and everyone you see.

Because the Dart Gun only holds one round and fifteen or sixteen on reserve, you will likely need to find more ammo; fear not, additional ammunition can be purchased from the Arms Dealer for a relatively cheap cost. In the end, once thirty NPCs, hostile or pedestrian, have been knocked out with the Dart Gun, the achievement will unlock.