M2 Browning

The M2 Machine Gun, or Browning .50 Caliber Machine Gun is a heavy machine gun. It was nicknamed "Ma Deuce" by US troops or simply called "fifty-cal." due to its caliber.
John Moses Browning (1855–1926) of Ogden, Utah, was the inventor. His military arms were considered to be outstanding. German Field Marshal Hermann Göring said, "If the "Luftwaffe" (German Air Force) had the Browning .50-caliber, the Battle of Britain would have turned out differently". 
Browning began work on the .50-caliber machine gun in July 1917 and it was introduced in 1918. It was a belt-fed, automatic weapon that came in both air-cooled and water-cooled versions. The gun was capable of single-shot or fully automatic fire. The U.S. Army, Army Air Forces, and Navy all adopted it immediately. 
The Browning .50 caliber machine gun has been used as a vehicle weapon and for aircraft by the United States from the 1920s to the present day. It was used during World War II, the Korean War, the Vietnam War, as well as during operations in Iraq in the 1990s and 2000s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. It is still in use today, with only a few modern improvements. Right now, it is the longest serving machine gun in the US military.