We use a paintball gun to keep the unwanted cats from our yard. They get hit a few times and realize that our yard is no fun. Honestly I don't understand these people who think it's ok to let their cats run free. As far as I am concerned they are now feral cats not pets. They piss and crap in MY yard! I will not have that. I have a cat and love her, but she is kept inside where she belongs. Some of the cats I shoot are my friends cats and she knows it. I know it's not that cats fault it's owners don't take care of them, but I will have no part of them.