Our "guard cat," Smokey, is large enough to scare off even the most ferocious dog. In fact, he's bigger than most household dogs.
He's just a plain old alley cat, but he weighs in at 31 pounds. Our vet says he's the largest cat he's ever had as a patient. Smokey is diabetic and gets an insulin shot twice a day. For being so big, he is very docile when it comes to getting his shot. He jumps up on his special table twice a day and submits to the needle without a quiver.
Smokey is almost 10 now. He was catnapped when he was about 6 months old and was gone for almost a month. When he returned home the pads on the bottom of his feet were bleeding. Since that time he's most comfortable when he's close to a member of his "family."
He guards us and our gardens diligently.