Thinking of gettin a guard dog?

I would definitely go for an English mastiff or a Bull Mastiff. THey are the sweetest dogs. They are 100% completely devoted to their owners and will do anything for them. THey are also sweet to strangers; however, when someone unwanted enters the house they instantly turn aggressive. Generally they bark a couple times (which is pretty intimidating) and then they will attack. They make great family guard dogs b/c they are essentially gentle giants. Unless of course someone they don't like enters the situation.