What other dog is as pretty and looking impressive and great guard dog beside the mastiff?

i like the mastiff but some people say they're not a great whatch dog,,, i like the look and the physicall presence of it.. i want a dog that looks and impressive like the mastiff a dog that will protect my house and my family bear on mind i m not looking for a killer dog cause i have kids,,,, so please tell me what dog breed any of you know of you can suggest me