Molotov Cocktail

"Molotovs, hell yeah!"

- Louis

"Momma told me not to play with fire, but..."

- Rochelle

"All right, cocktails!"

- Francis

The Molotov Cocktail is a thrown weapon that engulfs an area with flames for approximately 15-17 seconds. The area of effect is quite large and spreads over time before self-extinguishing. The fire will burn all Infected that come into contact with it. While Common Infected cannot attack after being ignited and die in seconds, Special Infected can withstand the fire until their health is burned away. The Molotov cocktail is dangerous in close combat because the splash damage and flames may cause you and nearby teammates to lose health. While it is burning, it can ignite other combustibles such as the gas can, the propane tank, and the oxygen tank. Molotov cocktail has a wick held in place of a bottle cap, the wick is soaked in flammable liquid like paraffin or alcohol. The bottle is filled with gasoline as the fuel. Once the Molotov cocktail is ready, it's wick is set aflame before before hurling at the target. The bottle breaks upon impact on it's target, spreading it's source of fuel; it also ignites the cloud of gasoline droplets and vapor which causes a chemical reaction. This results in a raging ball of fire consuming the source of fuel until it is extinguished or the source of fuel runs out.

Survivors

 * Throwing a Molotov at a wall or tank does not break it; it must hit the floor.
 * In versus games especially, conserve at least one Molotov for the tank. Make sure it hits, otherwise, don't be shy in using them to stop hordes that come from behind you. However be mindful of the position, if your team is using shotguns in a wide open area, and a wily smoker can pull someone past the flames, they're most likely incapped, if not worse.
 * Molotovs bounce off walls slightly, making a chance to run away from the flame or throw it around a corner, not exposing yourself.
 * Do not throw Molotovs in front of you, unless there is a tank. Most likely scenario is that you'll cause your team to wait it out, giving the infected and special infected some well needed time to spawn. Worst case scenario; the Molotov someone in your team threw in front of you means death to one or more of your team, due to needing to wait in a hard to defend spot.
 * Do not hit teammates. If they are incapacitated inside a fire, it may be difficult to revive them.
 * Where the Pipe Bomb is less effective (e.g. against Special Infected) due to its fuse, the Molotov shines. Setting a Witch on fire will gradually burn her health away and make her move extremely slowly, making her easier to kill. A burning Tank will survive for 30 seconds on normal, 40 on advanced, and 45 on expert. Only in campaign and survival modes, setting the Tank on fire will increase his running speed, since he doesn't have much time to attack the Survivors.
 * Though it may seem like a good idea to light a Tank up in single player, the end result is usually the same: three dead bots and a lonely Survivor. Bots tend to ignore fire altogether, wading through it like a very hot day in the park, and will continuously shoot at the Tank, burning or not. A better strategy is to focus your gunfire on the beast, even on Expert. Often, only one or two Bots will be dead, and you can continue on to the safehouse.
 * Burning a witch with said weapon is rather risky, as it takes quite some time to kill, but when playing Left 4 Dead 2, burning the witch then running with adrenaline makes killing a witch a walk the park.
 * No Infected of any kind know better than to avoid fire and will gladly cross it to reach you. The crux of the Molotov strategy is to let them. If you know where a Horde is coming from, throw the Molotov at a choke point between the Horde and your teammates. The flaming barrier will burn all Common Infected as they try to cross it. Try to throw the Molotov just as they reach the choke point in order to increase the likelihood of burning the entire Horde before the flames expire. Note that sometimes they will try to find a way around the fire, but it is not likely. Infected tend to want to get from point A to point B in a straight line unless a static object is in the way, like a big tree trunk.
 * Obviously, fire does not burn in water, though alcohol fires can burn in water. However, if you throw the Molotov at the edge of the water(on riverbank), it will still burn on the water all the same.
 * There is at least one exception to this: Death Toll's first Crescendo Event in the storm drains. A Molotov thrown into the shallow water will burn as normal.
 * Also, despite the way water affected molotov in Left 4 Dead, it does not seem to affect them at all in Left 4 Dead 2. The many water-filled areas of Swamp Fever and Hard Rain can still support molotov fire. Even the heavy downpours in the Hard Rain campaign cannot douse the flames.
 * Once lit, Special Infected do not self-extinguish. Unless the map has water on it (e.g. Death Toll Finale). They will burn until they die. This applies for Tanks and Witches, too.
 * In Versus, if a player is hanging and being attacked by a Smoker out of reach from normal weapons, consider lobbing a Molotov to release them, if you cannot even attack the tongue.
 * Since the Molotov will not set off car alarms, a common strategy is to lob a Molotov at a car alarm to kill any Smokers that would try to pull you towards the car (which will set off the car alarm).
 * When on the Rooftop Finale in the No Mercy campaign, when you get to the ladder, you can, rather than just lobbing a Molotov onto the roof, climb the ladder and check where the Infected are. Usually there's a Smoker south-east of your position. Lobbing a Molotov there from the elevator shaft should get rid of a Smoker, thus leaving a Boomer and two to three Hunters on the roof to deal with. This takes a lot of practice and should be practiced on in single-player with cheats on.
 * Some players have developed a method to use Molotovs to kill every Infected around them. This tactic is know as "Ninja Molotoving", where they throw a Molotov directly at their feet, killing the Infected surrounding them. This isn't wise, as it puts you directly in the center of the inferno, although this is a good way to escape a surrounding horde, as long as you don't mind losing some health.

Infected

 * Though it will eventually kill it, the Hunter does twice the normal damage when it is on fire. Note that after the recent update, the bonus fire damage is only gained by lighting a Hunter on fire using a Molotov. The Hunter doesn't deal as much damage as it used to after the update as well.
 * As a Boomer, you can set yourself on fire to become a ticking time bomb. Run into Survivors to forcefully explode, since the Survivors can't safely push you away and shoot you without the risk of being exploded on. However, Boomers don't have very much health, so don't set yourself on fire too early.
 * If you're playing as a Smoker, a great tactic is to drag a Survivor through the flames, causing massive damage and preventing others from rescuing them. Take care as they can kill you with their weapons; flame doesn't burn bullets.

Left 4 Dead 2
In Left 4 Dead 2, during the Dead Center campaign, using a Molotov or incendiary ammo on the Infected that are wearing Hazmat suits will have no effect.

Behind the Scenes
An early screenshot shows that the Molotov was grey and had a different-shaped top before becoming the final design.