A blowgun with office-type pushpins might be effective. I've discouraged some pests around here with this arrangement. The pushpins, surprisingly, fly point first. Just don't inhale with the pushpin in your blowgun, and remember they will slide out if you are aiming downward.
Kind of a rainbow-ish trajectory, but they will usually penetrate the feathers to give a mild sting, and are non-lethal, cheap, and have a restricted range. And if somebody finds a "spent" pushpin on the ground or sidewalk, it's no big deal. I use them for indoor practice --just to watch my groups.

When I lived in a single house, I got an 80lb pistol-type crossbow for this purpose but got a rush of brains to the head and realized those bolts would be pretty obvious if found. Besides, the crossbow was surprisingly noisy. So was the bolt impact if it hit something solid, like my back fence. I was thinking of getting a slightly longer string for it to reduce its power and noise, but never got around to it.