Laser Sight

The Laser sight appears in Left 4 Dead 2 as a tool used to enhance the targeting on all weapons. The laser is the concept of the LLM01 laser sight. The laser can be attached to any Primary Weapon. "Look guys, laser beams!"-Ellis

The laser sight cannot be transferred to other weapons or the exact same weapon once the player changes their gun. An example is having a laser sight-equipped to an auto shotgun and picking up another auto shotgun; the new auto shotgun will not have a laser sight.
 * While having the laser equipped, it is possible to use your flashlight.
 * Other players can see your laser sight even when you are behind them making it easier for them to avoid stepping into your line of fire.
 * If equipped to a Hunting Rifle or Sniper Rifle, it makes no difference to its accuracy while stationary, but increases its accuracy while moving.
 * If equipped to the Silenced Submachine Gun, and the user is crouched and standing still, it will be as accurate as a Sniper Rifle when zoomed in.

Tactics

 * A laser sight improves all weapons considerably, but your best bet is to attach one to an AK-47 or M-16 - all guns that are powerful but inaccurate without any upgrades.
 * Laser sights are incredibly rare. Hold on to your life as long as you can when you have one and avoid swapping your weapon. If not all of the team have laser sights and a survivor with one dies, it is a good idea to salvage the weapon to take full advantage of the sight.
 * Regrettably, you cannot attach a laser sight to Sidearms. Only main weapons can benefit from a laser sight. This fortunately also means that you can swap your secondary weapon without losing your laser sight.
 * Using the Laser Sight on any shotgun is pretty much useless. It wont make your gun any more accurate than if you are standing still. However, you'll have more accuracy if you crouch.
 * Laser sights are incredibly useful in Realism mode, making it much easier for Survivors to find each other without silhouettes.
 * Laser Sights are infinite, so if you find a better weapon shortly after attaching one, you can go back to upgrade your new weapon.
 * Laser Sights don't increase the grenade launcher's accuracy.

Behind the Scenes
The laser sight was originally an upgrade in Left 4 Dead, but was unused in the final version. However, mods on the PC version allow the player to use upgrades, which lets players use the laser sight in Left 4 Dead.

Accessibility
The Laser sight is a very rare find. Players can often play most campaigns without spotting a laser sight at all. The only area that always has the laser sight is Whitaker's store. Swamp Fever also has a high chance of spawning laser sights if playing from start to finish. It can be found in any campaign though. Since the sight cannot be transferred from weapon to weapon, the ideal solution is to equip it to a weapon the player intends to keep. Usually, if the Director decides to spawn one, Laser Sights will only appear once per campaign. However, it has been reported on extremely rare occasions that two will spawn. Sometimes they will be in separate sections of the campaign, and other times it can appear in the same section of campaign.