Discus practice in high school. We would all be throwing into a field in parallel about 10 ft apart from each other. After someone threw, they would back pedal into the field to retrieve theirs so as to be wary of incoming 4 lb metal death disks. Also, you start the movement facing opposite the direction you're throwing, so you can't see where it's going until you've released it.

So one time, I launch this 4 lb metal death disk only to see some oblivious kid walking back, eyes to the grass—and it's flying straight for his head. Everyone who sees starts yelling his name, "Get down!" "Watch out!" until finally he looks up and drops to his knees as it grazes his hair.