Silent Roar Lion Manure
Silent roar lion manure pellets are soaked in the essence of lion dung then dried and sterilised. The idea is that cats will smell the much bigger cat and keep well away from the area. They should be spread 3 or 4 inches apart on your flower bed or other target area. Generally they will last a month or so, though with heavy rain their effectiveness can be drastically reduced as the scent is washed away.
Not always effective, but worth a try if you don't want to go down the ultrasonic or water repeller route.