I had neighbours for 15 years, who have now moved (thankfully!), who had two boys who just didn't get on.
They constantly threw things over my fence to deprive each other of possession. These included a metal letterbox, several house bricks, many toys, including a trike, a scooter and their little sister's dolls pram. I did not throw any of them back (too dangerous), but collected them up on a weekly basis and left them by their back gate, only to have them thrown over again. I tried confiscating them but they would just yell and yell over the fence, or try to batter down my back gate to get to them.
It was not safe to sit in the garden, the damage to plants was total and, although the parents shouted and screamed at them not to do it, it made no difference. I was so relieved when they moved.