Posted: 20/06/2013 at 23:41
the water pistol might let off some latent (human) aggression but unless you spray them EVERY TIME they come in the garden you may as well not bother as it won't be a consistent deterrent.
Tiger or lion poo doesn't do anything (but it allows zoos to make money charging chumps to take away their waste)
Really- nothing short of netting the place will work. If you think ultrasonic deterrents work, try amazon or ebay and get another one.