Do you just want a barker that will alert you to trouble?
My girls bark at anyone they don't know, even if they are across the street. They even come and "tell" me something is up and I gotta follow them to see what's going on. They are both retriever/retriever mixes (golden/lab I think).
I used to know a family with a Dalmation. While it was a gentle dog, it REALLY worried about kids and would pace around the swimming pool. And he was sensitive to one child's diabetes. I guess that's sort of a guard dog.