When it comes to automatic weapons many firearms comes to mind, The M2 (ma deuce), M249 SAW, M16 and other variants. But the first that comes to my mind is the German MG42.
The MG42 is the successor to the earlier MG34. The rifle was introduced in 1942 which is where the number 42 comes from. This machine gun was in service from 1942-1968. When they were updating to the MG42 from the MG34 they improved on the internal working components with a brand new locking mechanism. The gun was made largely from stamped parts which decreased production cost and time when the German army had a small arms shortage. The MG42 had an effective range of 1000 meters and fired a blistering 1,200-1,500 rounds per minute sounding more like tearing a piece of canvas that the allied soldiers feared. The designers made it fast and easy to change barrels, about six seconds for each change. The MG42 like the 34 was a very needy weapon system due to dirt and debris regularly jammed the weapon if unchecked. The MG42 was lighter than earlier era machine guns. The gunner could carry the gun with the front mounted bipod and his assistant gunner would carry the ammo. The MG34 and 42 threw down a storm of lead from the eastern front to the beaches of Normandy. This was a terrifyingly successful mounted or squad managed machine gun. The history of the MG42 is still going on. They may not manufacture this weapon or have it in full service in any nation but they have still made it around the world regardless of the fact. This weapon from WWII is still in people’s collection and is still spitting its fire around the world.