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 any zombie killer's desire with the ultimate in gore-splattering destruction. But the fun won't last long—once the gas gauge hits E (emptied), 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 can 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.

The Chainsaw is classified as a shredding weapon (the only weapon other than the Crowbar and Pitchfork to be classified as such), and will spew blood on your screen as it mutilates the Infected into body parts.

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-sceond 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—if held off long enough, the Tank would easily die, if not heavily damaged.
 * 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.

Pros

 * Fastest attacking melee weapon, and generally just the fastest attacking weapon, be it hitting 10 times per second dealing 100 damage, surpassing M60 at 9 times per second.
 * In terms of DPS, it is the most powerful weapon in the entire game, the M60 fires slightly slower, but then, it's significantly less damaging than the Chainsaw per attack.
 * Perfect against Hordes, the Wandering Witch (if done behind) and many other Special Infected, but be careful against Witches in Advanced mode or above—1.3 seconds to kill.
 * The chainsaw has a hidden resistance value against common infected when attacking, as stated in "z_hit_chainsawer_factor", the default value is 0.5, which means half damage received from common.
 * Probably the best melee weapon against a Tank, if you can distract him while the Chainsaw slashes him, this can be the best melee way to take him down other than the M60.
 * Makes constant noise, therefore, on Realism mode, this will help your teammates know where you are.
 * Easiest melee weapon to use against Special Infected due to the rapid fire rate; melee techniques used against certain Special Infected that otherwise require precise timing, such as cutting Smoker tongues or killing Hunters mid-pounce, can be performed simply by holding the fire button and aiming the weapon correctly, as you can just slice a Hunter when he pounces on someone, killing him.
 * The Chainsaw can kill Riot Infected from the front, this is likely because the Chainsaw's way of cutting can completely ignore the armor, unlike bullets and other melee weapons. While you won't usually find one in "The Parish" campaign, finding one makes fighting them significantly easier.
 * The Chainsaw will also attract and easily kill Fallen Survivors and Jimmy Gibbs Jr.
 * WIthout the help from teammates, using a Chainsaw is by far the only way to escape the Smoker besides killing the Smoker. As stated before, other melee weapons can cut the tongue, but the Chainsaw is the safest way to do so.

Cons

 * Limited fuel, gets discarded when empty, can't be refilled, limiting usage unless it becomes surprisingly common, or if the game gives it infinite fuel (Mods, Mutations, etc).
 * Long deploying time, leaving you vulnerable while switching weapons.
 * Is not useful to have if carrying a Special Tier weapon or weapons with low effective range like shotguns or the Grenade Launcher.
 * Creates a lot of smoke and covers your screen in gore, impeding your vision.
 * Heavy damage means the same with friendly fire, use with caution, unless on Easy, where friendly fire is disabled.
 * Noise attracts many nearby Infected, though this can be an advanatge when you are high on fuel, because most infected will melee you only to die on contact.
 * 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.
 * If empty, it will switch to a single Pistol, which leaves players more vulnerable unless they find a suitable surrogate, be it another pistol, a magnum, or a different melee weapon.