Chainsaw

"And if we run out of bullets.... Baby, they gonna wish we hadn't!"

"DIE, DIE, DIE MY DARLINS!!!! DIE, DIE, DIE!!!"

"YEEEEEAAAAHHHH!!!"

The Chainsaw is a close combat weapon introduced in Left 4 Dead 2. When used, it is held out in front of the Survivor, dealing heavy damage to any Infected in it's way and giving the worst injuries to Common Infected by far. However, the Chainsaw runs out of gas after about one minute of continuous usage, causing the Survivor to drop it and pull out a P220 Pistol. A Survivor cannot refill the Chainsaw.

Unlike other secondary weapons, the Chainsaw is a rather rare find, usually spawning out of the way, normally in the same areas that the Grenade Launcher can be found. The Chainsaw takes up a rather large area of the screen when out and a larger area when spinning, and does a lot of friendly fire damage.

When a Survivor is using the Chainsaw, Common Infected are attracted to them. Against most Special Infected, it's usually best to use your primary weapon, although you can kill a stationary Witch with the Chainsaw before she can get up and strike you. You can also hold out the Chainsaw to kill a Jockey or a Hunter before they can get to you.

Tactics

 * The main usage of Chainsaw should be preserved for Gauntlet events(if featured in level), where you have to rush forward as fast as possible, while the zombies pile up on you endlessly. Such an event is The Screaming Oak rollercoaster, as well as the strange alarm setup in second level of The Parish.
 * The Chainsaw's long rev-up time means that switching to it in the middle of a horde is a bad idea. Instead, find some cover before pulling it out, or just momentarily back to a wall and shove the horde back when revving up.
 * When covered in Boomer bile, the Chainsaw is a good option to rip through the incoming horde. However, the bile also makes it more difficult to watch for your teammates, so be careful, though you should inform your team that you're going to use your chainsaw in such a way and they should be wary. (Assuming they haven't been boomered aswell)
 * Keep your distance from other Survivors when using the Chainsaw so that you can avoid hurting them and make it easier for them to shoot Common Infected attracted to you.
 * When using the Chainsaw, it's usually best to pick up a primary weapon with good range, such as an Assault Rifle or Sniper Rifle, for taking out Special Infected.
 * A Bile bomb works well with the Chainsaw, making it easy to line up Infected for kills, however, aside from just clearing an area, the Bile bomb actually spawns additional zombies, which will attack the closest survivors to them, when the bile wears off and they have not been killed.
 * The chainsaw has limited fuel, so make sure your other weapon has a good reserve of ammo.
 * When fighting a Tank, using the chainsaw will usually result in you getting punched away, so wait for the Tank to be climbing a ledge or otherwise distracted before cutting loose on him. In Versus mode, use the chainsaw very warily upon the tank, as the tank has 270 degree melee attack, and the player operating the tank can usually hear a chainsaw easily.
 * The chainsaw is the only melee weapon that will allow you to free yourself from a Smoker's tongue while being initially grabbed, though this doesn't seem to always work, be it lag or a glitch.
 * The grenade launcher and chainsaw don't work too well together, because the chainsaw has a long rev-up time, while the grenade launcher has a long reload time, and both are hard to come by in a Campaign. In addition, both weapons do heavy friendly fire damage, and neither is very good against Special Infected. Aside from Versus, where the grenade launcher can be a great equalizer against Special Infected.

Trivia

 * The Chainsaw is modeled after the line of STiHL chainsaws.
 * The Chainsaw is a fairly common weapon of find at the first levels of Dead Center and Swamp Fever. There are hardly any chainsaws in other campaigns, though you may find one.
 * The Chainsaw seems to be Coach's signature weapon, as seen in the trailers, pictures, in the intro, and in Coach's bio.
 * CPU players will never pick up or use the Chainsaw. If someone takes a break while using the Chainsaw, the computer will drop it.
 * Oddly enough, if you pick up the Chainsaw in Commentary Mode, all nearby Infected suddenly become hostile and attack.
 * A rare glitch in the Xbox 360 version causes the top halves of Common Infected to float in the air with their entrails swinging around beneath them.
 * If you look at the chainsaw in the E3 trailer, you can see what looks like: '22" HALE PRO'. "HALE" may be a reference to Saxton Hale from Team Fortress 2.
 * The Chainsaw can kill Riot Infected from the front.
 * In Horror media, the Chainsaw is the most popular weapon for use in a Zombie outbreak, despite being very impractical and dangerous to use.; making it more of a suicidal charge weapon. Even in horror media, the weapon is demonstrably ineffective. The Zombie Survival Guide trailer shows the chainsaw taking a good two to four seconds to get through just two common infected and a Smoker's tongue. Obviously, this sort of time commitment would be suicide in real life, or even in game.
 * If you kill a Common Infected with another weapon, then attack them with the Chainsaw as they are dying, the death animation will still play, even if the lower half of the Infected is gone.