Launcher

Launchers are projectile weapons that fire an explosive projectile other than a bullet.

Overview
Launchers have many different purposes. They can be used as indirect fire support on a squad level. they can be used as anti-armor which have heavier shells or rockets to penatrate thicker armor, anit- personal, which is used to take out human targates,and anti-air, which is used to take out flying vehicles. The different types are as follows:

Grenade launchers: lobs special grenades in an arc shaped pattern; can be slung to the underside of a rifle's foregrip using the rifle's magazine as a handlegrip; also, fully automatic GL's can be mounted on a tripod or helicopter to provide fire support

Unguided RPG: Fires ungiuded rockets to destroy targets

Guided RPG: fires lock-on missles to fly at targets; can be in Direct or Top-Attack profile flight.

In MW2
In Call of Duty: Modern Warfare 2, launchers have been classified as a secondary weapons. The launchers that are in this catagory are:

AT4

Thumper

Stinger

Javalin

RPG-7

While this is an attachment rather than a stand-alone weapon, the M203/GP-25 is also classified as a launcher.