I like the idea of the paintball gun, but a warning to your neighbors about the use of one may be warranted. Some people can be pretty picky about things, and the last thing I would want is for animal control to show up talking about animal cruelty for shooting one with a paintball gun. Those things can really get you, I got shot with my hubby's and it left a bruise on my leg for well over a month (he shot me from about 15 yards away, no joke) and the tenderness still hasn't gone away totally (this was back in late April). A small, inexpensive outdoor camera may be an option if you can afford it and depending on where your chickens will be, that way you have it on camera if something happens.