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 killed, it leaves 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. 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.

On an interesting note, if it is for some reason idle you can hear it hacking and coughing like real life smokers.

Specific Tactics