Kuba_T1000's airsoft minigun holds 16,000 rounds of plastic BBs, fed from an electric ammo pack. Made almost entirely with machined aluminum and powered by high pressure air (or CO2), Kuba's build is appears quite sophisticated, and flawless.
But the best part is his *free* detail rich tutorial on how to make your own.
See it the gun in action below!
For more images, visit Kuba's M134 gallery.