Actually, contrary to Pelle, I will say that the .50 BMG has more than proven its unofficial title as the worlds premier long range sniper caliber. The past two world record shots on human targets have all been successfully performed by rifles chambered to fire this effective round.
It all started with that sniper we all know and love, U.S. Marine Gunnery Sgt. Carlos Hathcock, who claimed the life of an NVA regular at 2.25km with the The Browning M2 .50 caliber Heavy Machine Gun. Impressively, the M2 has an estimated effective range of only about 1.83km.
Most recently, during Operation Anaconda in Afghanistan's Shah-i-Kot Valley, Master Corporal Arron Perry of the Canadian Forces, with a .50-caliber McMillan TAC-50 rifle, shot and killed an opposing combatant from a distance of 2.43km.
So, while the .50 BMG is utilized mostly for tactical materials destruction, and to spite the more common use of the .308, 7.62, and .223 cartridges, the .50 BMG has maintained a firm hold on its record for almost 40 years.