An SMG in service with the Anglo-Sino Alliance Military. Often seen in the hands of Alliance troopers.
(The prop for these weapons -- there are several variants -- is Heckler and Koch MP-5 series, very common SMGs in police and military service and a staple 'smg' of Hollywood. One of the more exotic versions seen has been the MP-5SD6 - the prop used could very well be an older model MP-5A3 modified with the new style trigger arrangement or, perhaps more likely, could be a Tokyo Marui Airsoft(approve sites)
-- a type of pellet gun, but an extremely detailed and gorgeous pellet gun.)