Too bad Australian Cattle Dog is not on the list. Our one is especially aggressive towards any stranger, and always barks at anything in the range of her senses.
I’ve read that about ACD’s, they’re on my list of possibilities if and when I get a dog.
For now, my cat rules the roost. And she is one heck of a guard cat, too! Some workmen were fixing the electicals on the side of the house once, as soon as they got near the porch she turned into a snarling, yowling monster. Which was quite a surprise, because she’s usually such a people-cat.
I have an Aussie and a Lab/Shar-pei cross. Both are guard dogs in the sense they have not been socialized to anyone unless we are around. I used to say “I pity the fool that ever breaks into this house” and I still believe that but we don’t get much company out in the country....