M60 Machine Gun

The M60 is a special tier weapon that made it's debut in the Left 4 Dead 2 DLC, The Passing. It carries only 150 rounds and after that's depleted, it is dropped. The Survivor will then revert back to their secondary weapon, much like with the Grenade Launcher.

Pros

 * Deals more damage, so killing Special Infected, mainly the Tank and Witch, is quicker.
 * It can mow down many Infected faster, thus making taking out a horde quicker and easier.

Cons

 * You can't refill the ammunition, so when you are out of ammo for it, it will be dropped.
 * It might be rare to find it with a Fallen Survivor and also might rarer to find around the levels just like a Grenade Launcher.
 * It might slow you down and might also impact your melee.