I am not sure if this is how it is supposed to work, or if its just glitched but I got this in the very first 2 minutes of the game. After you are told to put on your silencer and then the door opens, I cloaked, picked up the chair, and threw it at the dude whose back was turned. Someone came to investigate, and I threw the SAME chair at him and the cheevo unlocked. Please comment if you using the same object counts for you as well.