What Is The Greatest(Iconic/Legendary) Machine Gun In United States Military History?

My choice is the .50 Cal. Machine Gun also known as the Ma-Deuce. It is the second longest weapon used in the U.S. inventory preceded by the M911 .45 CAL Colt Pistol. It has various types of ammunition from armor piercing, ball, to tracer and more. Its history is second to none from WWI to Afghanistan. It did its job and has the record to prove it.
I trained on this weapon as an Air Defender and Motor Transport Operator for over 24 years. It is a power weapon. You can use it on just about any piece of equipment e.g, airplanes, helicopters, tanks, armor, vehicles and so on.
The .50 cal. machine gun was developed by John M. Browning at the request of the U.S. Army. Experience in France in 1917 showed the need for a heavy machine gun that could act against aircraft (fixed wing and balloons), tanks, and other armored vehicles that were then first appearing on the battlefield. Starting in July 1917, the Browning .30-06 machine gun was scaled up and reinforced to handle a .50 cal. cartridge, in experimental development from ideas used in a French 11mm machine gun. The first .50 cal. prototype was assembled by Browning at the Winchester plant on 12 November 1918 and Winchester went on to produce a total of six models for testing. However, Infantry tests were unsatisfactory, finding that the bullet lacked range and penetration while the gun was unstable in automatic firing.

The technical problems of the new .50 cal. machine gun were overcome when a captured German 13.2mm anti-tank rifle and its ammunition gave the Winchester engineers the ideas needed to complete the .50 cal. cartridge development with performance satisfactory to the Army. The completed Winchester-designed cartridge was taken to Frankford Arsenal (Philadelphia, PA) in 1918 for production. The prototype .50 cal. machine gun was altered and upgraded to work properly with the new .50 caliber round, resulting in the standardized .50 cal. United States Machine Gun M1921, adopted for use on aircraft in 1923. After a series of .50 cal. water-cooled, aircraft and tank models were tested in the 1920s, an improved version of the M1921 was adopted in 1933 as the air-cooled Browning Machinegun, Caliber .50 HB, M2.
Subsequent models of the M2 .50 cal., using the same receiver, were adopted by the various services in both air-cooled and water-cooled versions for use by infantry, aircraft, tanks, and otehr applications. During World War II, nearly two million M2 machine guns of all variations were produced.

The M2 .50 cal. Machine Gun went out of production in the 1970s, and by the early 1990s the capability to manufacture the M2 barrel had virtually disappeared from the U.S. industrial base. An Army inventory of 13,000 "unserviceable" M2s were stockpiled, although they required some level of repair or maintenance before they could be used. With combat operations in Iraq and Afghanistan, the Army identified a requirement for an additional 8,000 M2s for fielding in FY2005. During the summer of 2004, Anniston Army Depot began to repair M2s at the rate of 100 per month, with a ramp up to 700 per month by early 2005, once new barrels and other parts were procured.

https://www.youtube.com/watch?v=yuZ5VrLQ1ek

https://en.wikipedia.org/wiki/M2_Browning