In many of the staging areas on certain maps, there are a number of basketballs. They serve little purpose, other than to shoot around and kill off the thirty or so seconds before a match begins. This is where the user Puppy :U and a friend realized you can use Junkrat’s concussion mine along with a steel trap to effectively weaponize one of the basketballs. 

Watch as he manages to attach a trap then a mine to it. Once the door opens and the match begins, Puppy “dribbles” it along with a little burst fire and even jokes about possibly killing someone with it when all of the sudden an unsuspecting enemy Tracer stumbles through the wrong door at the wrong time.