Now, what do you get when you cross a boxer and a great dane? The Bullmastiff. They are large and have imposing figures on a lot of creatures. Although the bullmastiff can be very dangerous in general, it’s the males that you have to watch out for. Male Bullmastiffs tend to weigh up to 130 pounds so if you manage to own one, it is very important to train them for them to be obedient dogs. Just like the Boxers, Bullmastiffs are also natural guard dogs so you can expect them to be aggressive. There have been 2 incidents of Bullmastiff attacks on humans back in 2014, one of which killed a 13-year old boy in New Jersey after escaping.