Sometimes JD your posts are just right there...Nobody's mentioned cat condoms yet. This would solve the REAL problem. You buy the 12 or 24 pack of kitty concoms, sprinkle them randomly beside bushes on the outskirts of your lawn, and the issue takes care of itself after a while. You see, REAL manly cats will take advantage of the free protection because they don't wanna catch anything off those skanky alley cats that have been ridden like Seabiscuit on the final lap. Not to mention dodging alimony [or MILK MONEY as they call it], so it's a win-win. Doesn't cost much, no one has to drink delicious car fluids, and the population decreases naturally. Just don't get the ribbed, they don't hold up.
Seriously folks I understand the outdoor cats thing, I find it obnoxious and slightly mental.
Airsoft is the way to go, especially some of their full auto options, it's just so much fun laying down some suppressive fire with a full auto MP5...