The M-134 Gatling Gun can throw down 3000 rounds per minute. It's quite remarkable to see in action, especially when firing tracers at night. It's super lightweight, and mounted on almost anything. Now if they would only upgrade our assault cannons with different types of ammo. Incendiary, armour piercing etc. It would be nice to see some more flexibility in the assault cannon. My guess would be armour piercing would be rending, incendiary ignores cover saves, tracer rounds allowing a re-roll on night fighting distance.
Anyhow, take a look at the video, this gun is quite amazing. I would hate to have several of helicopters coming my way armed with these.