Not being a smart a** but the below pic is the 1st level of non-lethal deterrent within the home and when I go walking in the park. The one with the blue collar now weighs 120 the other 110.
When I was younger, I helped train protection dogs. The doberman I had back then was almost as big as the ones I have now. He stopped a couple issues simply by sticking his head out the front door and announcing his presence. We trained them to go for the hand with a weapon first (if there was one) and then a bite to the groin. Because we go camping and take them, I didn't do any training with these guys. They are crosses between Rhodesian Ridgebacks and Dobermans and are fearless when need be and gentle the rest of the time.
I walk these guys out front and on the road and let them be seen. Our immediate neighborhood has my dogs, one across the street as big as mine and a couple smaller ones. None of the neighborhood dogs are mean (not even mine are mean and will play with the neighbors and strange children) but none will let strangers enter the house without being let in.
I do think pepper spray is a viable option though and thank the ones that brought it up for reminding me that I need to go buy a couple for the family.