We have had several German Shepherd dogs from the GSD rescue. They will protect you no end, easily trainable, are loyal, they are smart and they will actually herd the toddlers when we have a bunch over. My 12 month old climbs all over them. But the hair.... it is everywhere

and it makes me crazy. Lots of people are afraid of them so people never bother me when I am out walking.
I had a black and white cocker spaniel growing up. Anytime someone got too close to my mother and the dog was around the dog would attack. He would go nuts. They very told us that they are so inbred at times that they can be very mean.
Our neighbor had Jack Russell Terriors. These dogs would KILL neighborhood cats, squirrels and terrorize any kids if they got out (which would happen all the time through their craftiness).