The M2 has been used by the United States in almost all its conflicts since its production. The long list includes WW2, Korean War, Suez Crisis, Vietnam War, Iraq War, Invasion of Panama, Somali War, War in Afghanistan, etc.
As an anti-aircraft weapon on ships, as many as six M2 guns can be mounted on the same turret. While on the ground, the M2 is used in either twin or quadruple mode.
The AN/M2 and AN/M3 variants have been put to use on US pursuit aircraft like the P-51 Mustang, P-38 Lighting, P-40 Tomahawk, etc. during WW2 and F-80 Shooting Star, Thunderjet and Sabre in the Korean War. Other aircraft variants include XM213, GAU-15/A, GAU-21A, and M3P.
The M2 is even used as a sniper rifle when equipped with a telescopic sight. This was a common technique during the Korean & Vietnam Wars when such an aggressive weapon was combined with a sniper scope. The US Marine Corps sniper Carlos Hathcock is credited for the practical use of this technique as he used his M2 to take down targets over 1800 meters away, twice the range of an average sniper rifle of the time!
When the IRA used the .50 Caliber Machine Gun in Northern Ireland, the media gave the weapon worldwide notoriety as a gun for Snipers.
The Unit Replacement Cost of the standard M2 Machine gun is around $14,000.
The M2 Machine Gun is used by almost all countries which are not under an arms embargo from the US. M2HB is the most sold variant of the .50 Caliber Machine Gun.
During the design phase and initial prototype development, the power of the gun was so paramount that it was restricted to experimental use only right until 1937. Surely, the M2 Browning is one of the best machine guns ever.