How about ammonia? That's how my neighbor got rid of skunks in his back yard. Smelled for a few days, but dissipated and no skunks.
I wish there was some way I could keep the neighbor's cats out of my yard.. I've tried everything including yelling at her, but she keeps telling me that it's too hard to keep her cats inside (she has 3, I have .. uh, more than 3 and mine NEVER get out except for 100% accidentally like a window screen that pops out of the window due to a microburst). They're terrorizing my poor birdies I feed outside...