Chainsaw

"DIE, DIE, MY DARLINGS!!!! DIE, DIE, DIE!!!"

- Ellis

"HELL YEAH!"

- Rochelle

The Chainsaw is a special close combat weapon, introduced in Left 4 Dead 2.

Official Description
Realize every zombie killer’s dream with the ultimate in gore-splattering destruction. But the fun won’t last forever—once the gas gauge hits E, it’s useless.

Melee Mechanics
Just like other melee weapons, the Chainsaw replaces your pistols in the side-arm slot.

As always, any melee weapon has to be used in conjunction with the primary weapon to form an integrated weapons system. Unlike pistols, passive close-combat weapons (such as the Nightstick or Katana etc.) never need to be reloaded, nor do they break or lose their edge. Melee weapons have limited reach along with a set rate of fire, and cannot be relied upon entirely; some infected such as Smokers and Spitters usually must be engaged with ranged attacks.

The Chainsaw, however, is an exception to the above. It is an active close-quarter melee weapon that can cause massive damage to Infected—as well as friendly fire damage to nearby Survivors caught in its arc. This factor is especially serious on Advanced or Expert difficulty where even brief contact with another survivor will cause significant damage. The Chainsaw runs off an internal fuel tank that cannot be refilled, meaning that it will eventually run out; it must be reserved for the most suitable circumstances (e.g. the bridge dash finale in "The Parish").

Damage-wise, the Chainsaw is the weapon with the highest damage per second. Therefore, allowing it to slay a Tank quickly, because of its 1000 DPS, taking 3/4/6/8 seconds (Easy/Normal/Advanced or Versus/Expert) to kill it. The Chainsaw can kill the Witch on lower difficulties before she is startled (the standard Witch on Normal, and the Wandering Witch on Easy), and a Common Infected in just one hit anywhere on the body (similar to other melee weapons). The Special Infected generally need less than half a second against the Chainsaw, aside from the Charger which takes just over half a second. Tactically it is not recommended to melee the Boomer or Spitter as the acid released on their deaths affect the radius of their corpse and the melee weapon positions a player close enough to be hit. If you start attacking with the Chainsaw and run into a stationary Witch, the time it takes to kill her is enough before she gets startled. If you fail, a teammate can easily finish off the Witch because of the significant damage already dealt.

Tactics

 * The Chainsaw is a powerful weapon and can quickly kill any Special Infected (except the Tank). In fact, the Tank is the only enemy that requires several seconds to kill, as opposed to the less-than-a-second time for any other enemy, and Witches, who often need a second to kill.
 * The Chainsaw is the only melee weapon that will allow players to cut themselves free from a Smoker's tongue before being grabbed whilst the tongue is still in the air and immediately after being grabbed while the Smoker is just starting to exert his pull. Other melee weapons can do likewise but require very precise timing and aim. However, the Chainsaw does not require any particular aiming nor such precise timing; simply using the Chainsaw either immediately before or after being attacked on the Smoker's tongue will shred it.
 * Primary weapons should be used against Boomers and Spitters on account that the acid has already been released when they are killed and you are sufficiently made distance.
 * When covered in Boomer bile, the Chainsaw is a good option to cut through the incoming horde. Communicate with similarly blinded teammates to minimize the risk of cutting them accidentally in the melee.
 * If you have been surrounded by the acid and by common infected, you cut your way through the horde easily due to the chainsaw's impressive power and speed and escape from the acid.
 * Be careful against Tanks and other Special Infected that can pin or knock a player down. In such cases, the Chainsaw speed drops back to idle and must be revved up again in order to be used, during which the player is vulnerable for a long period of time in the face of a serious threat.
 * When fighting a Tank, using the Chainsaw usually results in being punched away. The Chainsaw is therefore effective when the Tank is distracted (e.g. when another Survivor operates the mounted gun) — if held off long enough, the Tank would easily die, if not heavily damaged.
 * One exception is when near an incapacitated teammate and on a same level. In this case, a Tank's attack (except in Versus) will only pond on the incapacitated survivor and the Chainsaw can be used against the aforementioned Tank without risk. This must be done quickly, however, as the Tank can kill a downed survivor in 4/3/2 hits in easy-normal/advanced/expert difficulty.
 * Fuel conservation is a key requirement, so briefly tapping the primary fire when using the Chainsaw against small groups of Common Infected is essential to get the most use out of this weapon.
 * It is essential to keep a close watch on the amount of gas left in the Chainsaw's tank and be prepared to ditch it if running low and a good replacement high-tier weapon comes into view. The only good news is that the Chainsaw does not use any fuel when idling.
 * One idea is to regard the Chainsaw as a last-ditch weapon for use at the end of a map where a Crescendo Event is known to be coming up soon. Putting the Chainsaw player at the front of the team when charging hard for a safe room brings the odds firmly down in favour of the Survivors. This approach also has the benefit of allowing the Chainsaw to be ditched without risk to the team or player once everyone is within reach of safety. Once rescue arrives, you can then easily saw your way through to the rescue vehicle.
 * Due to its loud noise, using the Chainsaw will attract nearby Common Infected.
 * One of the worst situations to be in is when the sounds of the chainsaw has attracted a lot of Common Infected to attack you and the chainsaw is running low on fuel. This will cause trouble as you may not be able to eliminate an entire Horde in time.
 * However, in at least two instances, the noise may actually be used to attract the Common Infected AWAY from important objects, such as cars that still have their alarms active.
 * However, the noise of a deploying chainsaw attracting nearby Common Infected can be very beneficial at choke points that would otherwise be dangerous, acting as a short range pipe bomb to pull and funnel an idling Common Infected horde through a doorway. This can make exiting safe rooms and transitioning from low spawn spaces to higher spawn spaces safer (Such as exiting a building) with proper coordination.
 * The Chainsaw has a long deployment delay during which time it must be revved up to full operating speed. This reduces its effectiveness when a player is closely surrounded by a Horde. A better plan is either to fire up the Chainsaw in good time beforehand, backing away momentarily or shoving enemies back when revving up.
 * Keep your distance from other Survivors when using the Chainsaw to avoid hurting them and make it easier for them to shoot Common Infected attracted to you. This is especially important on higher game settings such as Realism when a hit from the Chainsaw can incapacitate a teammate.
 * When using the Chainsaw, it is usually best to pick up a primary weapon with good range such as an Assault Rifle or Sniper Rifle. This enables a player to take out Special Infected and pull off distance shots.
 * The Grenade Launcher and Chainsaw are an impressive combination of weapons in terms of sheer power, but they do not work well together unless your friends provide fire support. The Chainsaw has a long rev-up time while the Grenade Launcher has a long reload time and can only fire one shot before having to be reloaded. Both are also difficult to find (Though both are also common in "Swamp Fever"), and they are non-reloadable once their gas and grenades have been expended. Both weapons can cause heavy friendly fire damage and, in the Grenade Launcher's case, heavy damage to the user, with the potential for either an accidental suicide or an accidental incapacitation.
 * A Bile Bomb works well with the Chainsaw, making it easy to line up Infected for kills. Be prepared to kill the extra Common Infected summoned by the bile, however.
 * When trying to kill a Wandering Witch with a Chainsaw, be sure to attack her from behind so that she must turn before being able to retaliate. This will buy enough time to kill her. If you fail, the Witch still can be finished off by others easily.
 * The Chainsaw's size, the amount of blood generated and its exhaust smoke can heavily impede vision and cause a degree of disorientation resulting in a player taking more damage than would otherwise occur using a different melee weapon. This risk is accentuated when standing still and closely getting pressed by enemies. Computer lag may also become an issue for some players in such situations. It is therefore a good idea to keep moving and shifting position (even slowly), use melee shoves to clear space, stay calm and keep a steady aim.
 * When holding the Fire button with the chainsaw, the player takes half damage from a Common Infected in any direction which can be useful on higher difficulties.
 * The Special Infected still deal full damage to the Survivor who is currently attacking with a chainsaw.

Pros

 * High attack rate and DPS.
 * Extremely easy to use.
 * Spawns in any campaign, albeit much more rarely than other melee weapons.
 * Engine idle sound can allow allies to keep track of user.
 * Attacking attracts common infected, allowing them to be easily killed.
 * Easily cuts through a Smoker's tongue.
 * Grants 50% damage reduction to Common Infected attacks when holding the Fire button with the Chainsaw.

Cons

 * Ammunition cannot be recovered. When depleted, leaves the user vulnerable.
 * Long deploy delay.
 * Low spawn rate.
 * Attacks seriously impede user vision.
 * High DPS can easily kill allies with friendly fire.
 * Not recommended for killing Boomers due to bile showering attacker and any nearby Survivors, though if that happens, the Chainsaw can fend off the resulting horde and the user effectively distracts other infected with the bile.