For those who don't like to have cats in their gardens, I'll let you into a little secret. Cat's love cayenne pepper! One sniff and they leap into the air for joy, then do a little dance and run around like mad things. The thing is that they won't run around on the land that is covered with the divine seasoning so if this is your garden then you have a result. You're happy and the cat is happy (apparently) 
Oh, and if they dig up your rockery, just plant cocktail sticks in it 