Left 4 Dead 2/Weapons

Tier 1 Weapons
Tier 1 Weapons are primary weapons found early on in a campaign. They are also commonly found in safe rooms. Players rescued from rescue closets will only hold Tier 1 Weapons even if they were holding a Tier 2 weapon before dieing.

Pump Shotgun
Shorter range than the Chrome, but much greater spread as well as two more pellets in a shot. Like any Shotgun, it is great for taking out a horde at close range as well as clearing out infected indoors. Its relatively slow rate of fire means you can better control your ammo usage as well as fewer friendly fire incidents. Its wide spread and short effective range means that you'll have difficulty dealing damage beyond close range. Its slow rate of fire as well as having to reload each shot individually makes it harder to deal with a lot of infected or a fast-moving target.
 * Clip Capacity: 8
 * Total Ammo Capacity: 8 + 56 (64)

Chrome Shotgun
The Chrome Shotgun is the other Tier 1 shotgun. It has the tightest spread of any shotgun, though it has less pellets per shot compared to the Pump Shotgun but more damage per pellet, which makes it deal less damage compared to the Pump Shotgun. The tight spread makes it much more effective against infected in mid-range. Other than that, it can do what any other shotgun does, clearing infected indoors, taking out hordes in chokepoints and cr0wning the Witch.
 * Clip Capacity: 8
 * Total Ammo Capacity: 8 + 56 (64)

SMG
The Submachine Gun and it's silenced variant is the alternate choice to the powerful but slow and limited to close-range Shotguns. It deals weak but noticeable damage to compensate for it's fast firing rate. It excels at close to midrange targets, though suffers from poor damage and bullet penetration. When using this weapon, remember to fire in short bursts. While it might have a large ammo capacity, just holding the trigger button and mowing down infected will leave you with little to no ammo halfway through the chapter. Therefore, most experienced players manage their ammo carefully and fire in quick bursts. Only go full auto against a horde, a Tank or a startled Witch.
 * Magazine capacity: 50
 * Total ammo capacity: 50 + 650 (700)

Silenced SMG
The Silenced SMG inflicts more damage than the normal Submachine gun, but is less accurate at longer ranges. Like the SMG, it has a very high rate of fire. One of the most common Tier 1 weapons, it's damage is high enough that a short burst will easily kill a Common Infected, and while it's less accurate than the SMG, it still performs relatively well at mid-range. Burst firing and fire discipline is useful for conserving ammo for larger threats like Tanks and hordes. Once you attach laser sights to it, it becomes the best Tier 1 weapon and one of the best weapons overall, doing great damage as well as being very accurate.
 * Magazine capacity: 50
 * Total ammo capacity: 50 + 650 (700)

Tier 2 Weapons
Tier 2 Weapons are generally more uncommon than Tier 1 Weapons, and they're typically found about halfway through the later chapters. Tier 2 Weapons are generally stronger variations of Tier 1 Weapons, though picking up one is advisable if you have a Tier 1 Weapon.

Tactical Shotgun
The L4D2 version of the Auto Shotgun from the first game. It has a wider spread and more pellets per shot, but less damage per pellet than the Combat Shotgun. The Tactical Shotgun is possibly the best weapon for dealing with threats at extremely close range. It has a high rate of fire, good penetration as well as a large clip. While holding the mouse button let's you fire it semi-automatically, tapping it quickly actually makes it fire faster. Like any other Shotgun, it's good for taking down hordes and cr0wning witches, but the Tactical Shotgun does these close range tasks the best, though it suffers more at longer ranges compared to other Shotguns. Finally, it's incredibly effective against the Tank, so much that there's a 15% damage penalty for using the Tactical Shotgun against one.
 * Magazine capacity: 10
 * Total ammo capacity: 10 + 90 (100)

Combat Shotgun
The Combat Shotgun is the Tier 2 variant of the Tactical Shotgun. It has a tighter spread and more damage per pellet, but less pellets per shot. Most of what has been said about the Tactical Shotgun applies here as well, though it's better at handling mid-range threats due to it's tighter spread. As a reminder, it shares the damage penalty against the Tank with the Tactical Shotgun.
 * Magazine capacity: 10
 * Total ammo capacity: 10 + 90 (100)

AK-47

 * Magazine capacity: 40
 * Total ammo capacity: 400 (360 + 40)

M-16 Assault Rifle
The M-16 lies in the middle ground between the AK-47 and the Combat Rifle, and is one of the most versatile weapons in the game. It's good for clearing out infected indoors, taking them out from a distance, taking out Special Infected swiftly and surviving hordes. It has a higher rate of fire than other rifles and reloads faster, though it does deal the least damage between rifles. Still, it's a very reliable weapon, valued for it's flexibility.
 * Magazine capacity: 50
 * Total ammo capacity: 410 (360 + 50)

Combat Rifle

 * Magazine capacity: 60
 * Total ammo capacity: 420 (360 + 60)

Fires in three-shot bursts.

Hunting rifle

 * Magazine capacity: 15
 * Total ammo capacity: 150 (135 + 15)

Sniper rifle

 * Magazine capacity: 30
 * Total ammo capacity: 180 (150 + 30)

More accurate than the hunting rifle.

Special Primary Weapons
These weapons take up the same slot as the other primaries, but are much rarer and more powerful compared to the others. They also have unreplenishable ammo, using it up means losing the weapon.

Grenade launcher

 * Magazine capacity: 1
 * Total ammo capacity: 31 (30 + 1)

This weapon appears in limited quantity in the campaign, usually in a side room off the main path. It cannot be refilled at ammo piles, but has enough ammo to last through a given level.

It can be found in stadium in The Concert, the final area of the Dark Carnival campaign.

Pistol
The regular pistol, with a new skin, from the original Left 4 Dead. (This game's pistol is a P220, and a Glock when dual-wielding). Like in the previous game, the pistol can be dual-wielded. If you trade your two pistols for a melee weapon or a magnum, you will only be able to trade back for a single pistol. It's a reliable sidearm, having infinite ammo, and can serve as a primary weapon for shotgun users.
 * Magazine capacity: 15

When dual wielding you will be able to fire 30 rounds instead of 15 as well as doubling your rate of fire. The only downside to dual-wielding is a longer reload time, but that is virtually negligible, and you should always take the second pistol if you don't want to take a Magnum or melee weapon.

Magnum
The Desert Eagle magnum has a smaller magazine capacity, but deals more damage—80 points to the P220's 36. Like the regular pistol, the magnum also has unlimited ammo. Its speed is usually a factor when deciding between two regular pistols or a melee weapon. One thing that is valued a lot is the ability to one-shot common infected without needing a headshot on any difficulty or in Realism, as well as retaining your standing accuracy while incapitated. It's rarer than a normal pistol and usually spawns where a normal P220 would have spawned.
 * Magazine capacity: 8

Melee weapons
The melee weapon will take up your pistol slot. While only working at short range, they inflict more damage and can generally take care of the infected as they are close up.

If you are knocked down, you will use a single pistol instead of swinging your melee weapon.

Baseball Bat
The bat is only available to players that pre-purchased the game, or players in the same server as a pre-purchaser. If a player has downloaded The Passing DLC, the Baseball Bat can be found as normal. It has average damage and swing speed.

Chainsaw
The chainsaw runs on gasoline and can't be refueled. It will only use gas when you attack with it. It is, however, arguably the most powerful melee weapon in the game, dealing 200 damage per half-second and able to kill a Witch in 2 seconds on Normal difficulty. It's so loud it draws common infected to you. As long as you have it spun up, Smokers can't even grab you, as their tongue is instantly sliced off.

Cricket Bat
This bat deals 500 damage per swing and has a relatively long reach, but swings rather slowly.

Crowbar
Deals 500 damage, and swerves the player's screen a bit upon swings. A standard melee weapon otherwise.

Combat Knife (German Version Only)
The combat knife is one handed and the player slashes vertically when attacking. This is one of a few German exclusive weapons that comes from Counter-Strike: Source. Anyone can use it as long as someone playing the German version is present.

Electric Guitar
The electric guitar is a large, two handed melee weapon. It takes up a significant portion of your screen, and can behead enemies.

Fire Axe
The fire axe is the typical red-headed blade on a stick. Like the electric guitar, it is two handed and can be used to behead enemies. It is quite common to find and one of the most reliable, if slow, melee weapons. It has an extremely wide swing, which can take out a lot of common infected in a single swing.

Frying pan
The frying pan is a one handed blunt object. It is fast, but cannot behead enemies. It can be found relatively commonly.

Golf Club
A melee weapon only available in The Passing.

Katana
The katana deals 500 damage and has a fast swing, but has a slightly longer cooldown time.

Machete
While only dealing 250 damage, the machete makes up for it with good speed and cooldown. The low damage doesn't make a huge difference to begin with, as common infected never have more than 100 health.

Nightstick
Also known as a Tonfa, this weapon swings extremely fast but deals less-than-average damage. Riot Infected will sometimes drop these upon death.

Pipe bomb
The pipe bomb is a throwable weapon. It emits a loud beeping sound to attract common infected to the grenade before exploding.

Molotov
The molotov is a glass bottle full of flammable liquid. It shatters on impact and ignites a large area for about 15 seconds.

Boomer bile
Boomer bile is a canister containing boomer bile. When thrown, it shatters and causes common infected to either approach the bile cloud or targets hit with the bile. The common infected will proceed to attack the bile in question.

First Aid Kit
A very important item, it heals you or your teammate for 80% of the damage taken, but never back to full health. Healing yourself or a teammate takes a bit of time, so it's not the best thing to do in the middle of a horde attack. You can use it to do a melee shove for as much damage as any other melee shove, but any other weapon is better for killing zombies. First aid kits always spawn in every safe room and campaign finale, though they sometimes spawn in the level itself like in first aid lockers. On Expert difficulty, most first aid kits are replaced with Pain Pills, so a first aid kit outside of a safe room or finale is very rare.

Defibrillator
The defibrillator is used to revive survivors who have died, even survivors who are in a rescue closet, as long as their corpse is still present. Holding it out will reveal a revivable teammates corpse with a red outline. Approaching the corpse and hitting any of the attack buttons will revive them while giving them 50 health. It is usually advisable to have one designated player carry the Defibrillator while others carry first aid kits, especially on higher difficulties and realism.

Pain Pills
Pain pills refill 50 temporary health that will degrade at a rate of 1 point every 5 seconds. It can be given to other survivors by pressing alternate fire. It will restore your normal movement speed as long as your restored health is above 40.

Adrenaline Shots
Adrenaline shots restores 25 temporary health and puts you into a heightened state. For 15 seconds, you will move, reload, heal, pour fuel, revive and switch between items more quickly, do not suffer fatigue from melee shoves, makes you immune to the slowdown effect by common infected attacks and let's you maintain your speed while wading in water. As a side effect, you will get temporary tunnel vision and your sound becomes monophonic, which makes it harder to determine the location of infected and other survivors.

Lasers
A laser is an accessory that is added to a primary weapon to improve its accuracy. It provides a laser dot when attached. Lasers cannot be attached to pistols, items, or melee weapons.

You can find lasers in white boxes, similar to the fragmentation or incendiary ammo boxes.

Fragmentation rounds
Fragmentation rounds explode on impact. A common infected struck with an explosive round will be killed instantly, and most special infected will stumble when hit. The only special infected that won't stumble is the Tank.

You can find fragmentation rounds within tan ammo boxes. They will either fill the current weapon's clip, or replace the ammunition.

Incendiary rounds
Incendiary rounds cause targets to catch fire.

You can find Incendiary rounds within orange ammo boxes.