what about a doberman pincher= is a dog of medium size, with a square body that is compactly built, muscular and powerful, giving it great endurance and speed. They are elegant in appearance, with a proud carriage, which reflects great nobility and temperament. Always energetic, watchful, determined, alert, fearless, loyal and obedient.
or the german shepherd
Is a strong, agile, well muscled animal, which is very alert and full of life and when the occasion demands, eager, fit and willing to serve as companion, watchdog, blind leader, herding dog, or guardian. They have built-in instincts for guarding the home, which is why they are considered to be one of the best guard dogs. Also their sheer size and deep powerful barks make them a great burglar deterrent.
or chow chow
medium in size, they have a keen intelligence, with an independent spirit and innate dignity giving this dog an aura of aloofness and it is naturally reserved and discerning with strangers.
like any of them