The XM214 Automatic Gun (aka the Minigun) was developed for use mounted in and on helicopters and light aircraft. Like most G.E. Gatling gun type weapons it has six rotating barrels and the potential for a absolutely incredibly high rate of fire. It is electrically driven, and has a firing rate that can be adjusted from 1000 rpm all the way up to a unbelievable 10,000 rpm. In addition to that, it can be set to fire bursts from 30 to 1000 rounds. A real drawback to the higher rates of fire is off course the huge ammunition usage (166 shots per second) , and the power requirements, because firing it at full power it requires some 3.2 hp to drive the barrel assembly.

First seen in the movie "Predator" in 1987, the hand-held Minigun has captured the harts and minds of He-Men everywhere, be it in games or in real life. The very image of Jesse Ventura as Blain, spraying bad guys with a veritable hail of bullets that issued forth from his Minigun Painless was so powerful that the weapon has been seen in both countless other movies *and* in games.

Even in real life the idea caught on surprisingly well. Apparently some of America's Special Forces guys saw Predator and realized that a hand-held Minigun would be a great asset for clearing out landing zones real fast. Having ample access to the needed equipment, they started experimenting. And ran into some problems.
The first was that the Minigun weighed in at thirty pounds, which was heavy, but carryable. A backpack with a thousand rounds of ammunition and a linkless belt to the Minigun weighed in at another thirty-five pounds. Backpacks with two thousand rounds weighed in at sixty-five pounds, and were totally unrealistic in size. Just the gun and the ammo weighed in at sixty-five pounds.
The second was that in the movie, the power for the Minigun had been supplied by a pair of truck batteries through a cable that simply ran over the ground, and up into the Minigun. Since those batteries weighed some 30 pounds each, it was obvious that only one could be carried by one person (in addition to all the other equipment the soldier was to carry). Thus, the weapon could never be fired at its full rate of fire.
The third problem was that even at "only" a 1000 rpm rate of fire the gun produces about 11 kg of recoil *continuously*! And this amount of force increases geometrically in proportion to the rate of fire. Firing a large burst would result in the gunner being spun around by his own weapon, and spraying everything around him indiscriminately with bullets. Including his own comrades.....

After some experimenting it was thus realized that the gun would simply be too heavy and cumbersome to be ever used in real life combat, and the concept was abandoned. No army in the world has a hand-held Minigun in its arsenal.

 But, this was for real life. In games, where the gun-toting heroes all have physiques like Jesse Ventura and regularly mow down armies of enemies, a portable Minigun might be feasible. If we take into account that in recent years some manufacturers have made NiCad battery belts for use with Video cameras which weigh much less than truck batteries and can supply enough power to fire a thousand rounds at a firing rate of roughly 2,100 rpm before being empty, the weight problem is slightly allieved. Such a belt will weigh in at around six to eight pounds, as opposed to the sixty pounds for the old Truck batteries. It should be noted that such a battery belt would be completely discharged after firing a thousand rounds, and will require some three to four hours of recharging.
As for the recoil and aiming trouble, in a game a Game Master might simply give the user of such a weapon a appropriate penalty on his firing skills (if any, the weapon has Munchkin written all over it...), and be done with it.
With the weight of the weapon, ammunition, and power supply down to around seventy two pounds, the player gets a weapon which will fire a thousand rounds in less than thirty seconds, is large and ungainly, and is guaranteed to scare the crap out of anyone he points it at.

Note: Even in a game, this weapon is military issue only! Should you wish to use it in a game, you should keep in mind that not only will it be very difficult to find the weapon (in real life the military guards its Miniguns like they are made of solid gold...), but firing such a weapon with any degree of accuracy should also take inordinate amounts of skill, and the physique of a strong athlete.