[@MelonHead]

Well, versatility with firearms is a bit of a subjective thing. An "assault rifle" would be an intermediate cartridge select fire weapon. You got it mostly right but with the idea of superhuman opponents there are a number of variables that may need to be addressed as for the effectiveness of any individual weapon you choose to employ. Say you have an individual that has some sort of "Rock-like" skin. A 5.56x45mm assault rifle would be of limited use seeing as it's a high velocity small caliber projectile. Unless you used a sort of specialized ammunition, say, the US M995 "Black Tip" tungsten core ammunition.