The Smoker

The Smoker is an Infected with a long, whip-like tongue that can drag Survivors away from their team-mates and use its tongue as an organic noose to strangle Survivors when it is perched on a rooftop. Similar to Half-Life's Barnacle, or Resident Evil's Licker. When in danger, it can leave a haze of black smoke, distorting the Survivors' vision. Like most other boss infected, a melee from the Smoker does about 2 times the damage of the horde.

Tactics
One of the most deadly if the Survivors are being attacked by the Tank or the Horde. You'll need assistance from a teammate to un-noose you. The problem is that the Smoker is farther away than a Hunter would be. If enough smoke is billowing out, it could be hard to find the Smoker but the easiest tactic is to shoot it after it has lassoed a teammate because the tongue leads right to it. You cannot talk in smoke, only cough, choke, and hack.