.50 BMG

When people hear the word .50 caliber, most think of blowing someone in half two miles away. That's not going to happen. First, the .50 caliber isn't very accurate. You're not going to hit a human size target even a mile away. Second, who's going to be crawling through the woods with a 30 lb. weapon when a 15 lb. one will do just as good? However, if you're going to be taking out hard targets (tanks, aircraft...), the .50 is the way to go, nothing else beats it except a missile. It has an approximate muzzle velocity of 2,900 fps.
The military is probably the only organization that uses the .50 caliber, unless law enforcement needs to take out armor. Click here for more information on the .50, page by Hitach Industries, Inc.

Good for lightly armored vehicles and armored helicopters up to 1,500 meters.

The fuze in the Mk211 delays detonation of the main projectile charge until after penetration. This causes fragmentation inside the target for anti-personnel and fire start effects.