The Taiwanese company Autocopter has been building weaponized UAV's (unmanned aerial vehicles) since 2007. Their product may not be a Global Hawk carrying Hellfire missiles, but it is still lethal in an up close and personal kind of way.
The Autocopter Gunship is 8 feet long and weighs 55 lbs with empty gas tanks, and is powered by a 8 1/2 hp turbine. With standard tanks, the 60 mph machine could get 30 miles before turning back, and could get to 5000 feet.
The thing that makes it lethal are the two mounted Atchisson 12 gauge automatic shotguns. These guns are made of stainless steel and seem to be very reliable. Fed by 8 round stick mags or 32 round drums, they fire at the relatively slow 300 rounds per minute, so no selector is needed to control auto or semi-auto fire. With the long recoil system, there isn't much recoil, the better to control the helicopter, and they can also be fired upside down, and one is mounted upside down.
The choice of ammunition is buckshot, standard slug round and a British invention, the Frag-12 round. Frag-12's come in many flavors, and the most lethal is the armor piercing round which is a spin stabilized shaped charge warhead, designed to blast into armor plate. This does have the potential to make this bird a troublesome opponent, and changes the possibilities of the hobby helicopter movement. Even though the technical possiblities are quite interesting, it is also disturbing, having just read Daniel Suarez's "Kill Decision". These lethal flying machines have.... I'll let it go at that. You'll enjoy the story, but it may also keep you up at night.