Nightstick

The Tonfa (or Police Baton) is a new close-combat weapon introduced in Left 4 Dead 2. Not much is known about it at the moment.

The tonfa, like every other melee weapon, is not really meant to be used against Special Infected, because using it on a Boomer would cover you in bile, and killing a Spitter would leave you right in the middle of the goo. It would also take time to get to a Charger, Jockey, Hunter or Smoker. Against a Tank or Witch it would do little to no damage.

Trivia

 * The tonfa originated from either China or Indonesia, and was believed to have migrated to Okinawa due to the influence those countries had on Japan. In those times they were used to protect themselves from ninjas, but today is used by the police.
 * The tonfa can be dual-wielded in real-life, but it's unknown if it can be in the game.