The Mossberg 500 is a shotgun manufactured by O.F. Mossberg & Sons. Rather than a single model, the 500 is really a series of widely varying hammerless, pump action repeaters, all of which share the same basic receiver and action, but differ in bore size, barrel length, choke options, magazine capacity, and "furniture" (stock and forearm) materials.
In Game
The last shotgun to unlock, all rightfully so.
This shotgun has a much tighter spread then the SPAS 12 or the M3 and has a firing rate that can equal if not surpass the XM shotgun variant
Being a pump action gun it does have severe restrictions, as the cartridges are individually loaded which can be a pain as this gun runs through ammo at a alarming rate, combined with the fact that in the game you cannot shoot while reloading a pump-action shotgun.
Never fear, you overkill frenzy shotgun lovers, as a single shot will take down any target no matter what at close range, and lightly armored targets at medium range.
Though reported to be a US Army shotgun, it is mainly used by terrorists in game. It is also randomly sported by the shotgunner Rainbow soldier in the first level of Vegas 2.