Mk 19

The Mk 19 is an automatic grenade launcher originally designed to be used on U.S. Navy patrol boats during Vietnam, but was adopted by the entire military.

Call of Duty 4
In CoD4, the Mk 19 is used in Shock and Awe. It fires a semi-fast volley of grenades, but it can overheat. It's best to use it in small bursts as to prevent overheating. It's main use is to take out the enemy anti-aircraft emplacements and tanks throughout the capital city, but it can be used on infantry. Strangely, it won't harm allied soldiers. It's very powerful; it's able to destroy T-72 tanks with two hits and emplacements with one. However, you can't duck or hide while using it, meaning that you'll have to destroy enemies before they can hit you.