Grenade launchers are powerful weapons firing explosive rounds. There are some good ammo Attachments available, as well as the heartbeat sensor, and an Attachment that removes the "no criticals or headshots" effect of Grenade Launchers. There are only a few of these weapons, So we'll talk about each one individually.
EX 41: Holds four rounds, pump action, decent power, and shots bounce. Bullets explode on impact with a bad guy, and deal splash damage, so you can at least injure multiple enemies with one shot. If they don't hit anyone they explode about two and a half seconds after you fire.
M32: A very fun gun, With good RoF and ammo, allowing you to just cover an entire area with explosives. It is similar to the EX 41, but faster RoF and more ammo. And once you fire all twelve rounds, a fast reload gets you back in the game quickly.
Thumper: A strange grenade launcher, it holds 16 rounds that stick to people and walls or floors, and explodes after three seconds. because it does not explode on impact, it is easy to get killed before they even go off. The best method is to stick a bunch of bombs on the bad guy and run.
XM25: It hold four rounds in a clip, and has good damage. The bullets explode on impact, and they don't bounce. It is semi auto, and fortunately, the range is okay.