Chapter: St. Louis, MO: Widowmaker
During the Widowmaker fight in St. Louis. As soon as the battle starts, simply jump down on to the ground as soon as you can and move out in to the open area. There will be a clearly visible basketball hoop on the right of where you jumped down at on the wall, although you will need to avoid the Widowmaker to get it, as once you kill it this area ends and you won't have a chance again unless you restart the chapter.
Credit for the video goes to PS3Kevinnummer1 on youtube.