Grenade Launcher

"I tell ya, it's gonna be raining zombie pieces!"

- Coach "Time to make some zombie soup!"

- Nick

The Grenade Launcher is a primary weapon that made its debut in Left 4 Dead 2. When fired, it launches an explosive shell that kills Common Infected and weaker Special Infected. Any Infected that aren't killed by the blast are damaged and stumbled, except for the Tank, which doesn't stumble. It can only hold one shell, however, and has a long reload between shots.

The Grenade Launcher is unique in that it isn't found along with Tier 1 or Tier 2 weaponry, but instead is found somewhat rarely in side passageways and rooms, typically where the Chainsaw can also be found, though considerably less often. The Grenade Launcher can't refill its ammunition reserve with a normal ammo pile, meaning that the only way to get more grenades is to find another Grenade Launcher or use an ammunition upgrade.

Tactics

 * Friendly fire damage on the Grenade Launcher isn't too high on lower difficulties, but it definitely stacks up and gets higher with difficulty. Watch for your teammates whenever possible to avoid hurting them.
 * If surrounded by a Horde or if a Special Infected is about to grab you (Hunter, Jockey, or Charger), fire at your feet. The surrounding Horde will be vaporized or the Special Infected will most likely stumble or die as long as you're not concerned about taking some damage. Not recommended on higher difficulties.
 * Self-inflicted friendly fire damage for the Grenade Launcher was increased on the PC version of Left 4 Dead 2 on 9th June 2010 according to player feedback. It is still undergoing testing and may be changed accordingly in the future. Friendly fire on teammates from the Grenade Launcher is apparently unchanged.
 * Aim for surfaces to explode your projectiles upon. Fences that masses of zombies are trying to climb up or the walls of a tight room work well. The Grenade Launcher is less effective in wide open spaces as its grenades have a weaker explosion in comparison to a propane tank or Pipe bomb.
 * Usually, if shooting directly at a group of rushing Common Infected, you'll hit a few in the front, and only stumble the ones behind them. To get the most out of a single grenade, shoot from above and aim for the middle of the Horde to kill the most Infected.
 * The Bile bomb works well with the Grenade Launcher, as it makes it easy to bunch up large groups of Common Infected and get them at a safe distance to avoid friendly fire damage. However, be ready to clean up remaining Infected that don't bunch up.
 * The Grenade Launcher stumbles Special Infected that are pinning your teammates if it doesn't kill them. This can be used to save a teammate pinned at a point of no return or from far away.
 * If a Smoker starts to pull you, the Grenade Launcher always has the same accuracy even when moving, so you can easily land a grenade on him and save yourself.
 * While the Grenade Launcher doesn't do very much damage to a Witch, it does stumble it, meaning that if someone else disturbs it, you can stun the Witch to help them run away and make it easier for everyone to kill it. You can also shoot her to startle her from far away; this way your teammates can take her down very easily - a direct hit to the Witch stumbles her and cause about 550 ~ 850 damage.
 * With a direct hit, the Grenade Launcher does 1000 damage to a Tank. You can also use a Propane tank to make the Tank stumble while you reload, or a Gas can to light it on fire.
 * In addition to the 1000 damage per shot on a tank, incendiary grenades do not wear off on a tank. A player can use this as a make-shift molotov with a huge damage bonus.
 * In most cases, dual Pistols or the Magnum are better than the melee weapons, as they can allow you to not waste ammo on small amounts of Common Infected. However, sometimes it is better to have a melee weapon on back up rather than the Pistols for such cases as close quarter levels and for Hordes.
 * The Chainsaw isn't recommended as a secondary weapon, because they both share similar drawbacks. Both weapons cause high teammate damage (especially in melee), both have limited ammunition that cannot be easily replaced, both lack precision long-distance capacities, and both have long pauses during use (Grenade Launcher's reload and Chainsaw's draw time). Therefore you're generally better off with a more reliable secondary weapon.
 * The Laser Sight doesn't really benefit the Grenade Launcher, as it always fires forward in an arc with no damage drop off.
 * When using Incendiary Ammo with the Grenade Launcher, the upgrade will give you one extra grenade and when launched, it will set nearby Infected that did not die on fire, and a Special Infected that did not die will also be lit on fire. Using Explosive Ammo will give you a slightly more potent blast, although it is hard to notice. It will cause nearby Common Infected or Special Infected to stumble.
 * The Grenade Launcher can be used to detonate static explosives such as the Propane tank and Gas can. This can make it useful when setting up for a finale, although it makes the Grenade Launcher a hazard in Scavenge mode and in the finales of Dead Center and The Passing.
 * Use it as a support weapon - ensure that teammates with other weapons can cover you whilst you reload.

Pros

 * Extremely powerful
 * Can take down the Horde in seconds
 * Comes into its own in Survival Mode and during times when camping is an advantage
 * Works well with melee weapons
 * Can be useful with Incendiary ammo, especially against special infected, like the Tank and Charger.

Cons

 * There is no proximity fuse meaning that you can easily injure yourself with rounds that fall short
 * A huge calamity for friendly fire - a whole team can be taken down with one misplaced shot
 * Long reload time
 * Useless in close quarters situations or cramped buildings
 * Takes the place of weapons that could potentially do more damage
 * Hunters and Jockeys may be hard to hit due to their sizes and leaping abilities, however they're weak enough to be killed with a single shot.
 * Useless if equiped with Explosive ammo.

Achievements
This achievement can be hard to do in normal circumstances, but it can be easily done during a horde attack:
 * Firing at Infected climbing fences or walls.
 * Firing at Infected attracted by a Bile bomb or Pipe bomb.
 * Firing at Infected trying to attack you while you're on the rescue vehicle.
 * Firing at an ally surrounded by a Horde due to Boomer Bile.
 * Using an ammunition upgrade can also help.
 * Shooting at closed doors that have several Infected striking them. This can easily be achieved by hiding in a closet or similar enclosed space and throwing a bile bomb.

Videos

 * Swamp Fever Grenade Launcher Gameplay
 * PAX Dark Carnival Grenade Launcher Gameplay