many suggestions, none proved - get your own cat, get a dog, use a water cannon, get the high-pitched squealing machines, gets piles of lion poo, pave your garden....
2 litre plastic bottles [clear ones] filled with water, plastic forks in the flower bed, prongs upwards; both look stupid, but who cares, it's cut down on the gifts we get. Those metal cat signs with marble eyes, the local moggies crapped in front of ours!