The Colt M4A1 is a select-fire assault rifle and carbine version of the Colt M-16 rifle. It is the most common standard issued carbine of the world's militaries and law enforcement agencies.
In Mario Warfare, Mario fashioned a Colt M4A1 carbine as his primary weapon of choice when he and the other members of Smash Club engaged the Shy Guys who invaded the Mushroom Kingdom. He ran out of ammo and engaged several Shy Guys before obtaining a Beretta 92FS. The version that Mario was carrying was completed with a collapsible stock, a vertical foregrip, holographic sight and a handguard that was red and blue.