The cassowary, a descendent of the velociraptor, is widely considered the most dangerous bird in the world. Similar to the emu and the ostrich, cassowaries can grow up to 6 feet tall and jump-kick perceived threats with their lethally sharp, 4-inch claws. Cassowaries live in Australia, New Guinea, and the surrounding islands and can run up to 31 mph. They are also fantastic swimmers.