Nightstick

The Nightstick (or Tonfa) is a new close-combat weapon introduced in Left 4 Dead 2.

The Nightstick, 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.

This weapon is sometimes dropped by Riot Infected when killed

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 Survivors call the Tonfa a nightstick rather than a tonfa.
 * In the orignal Left 4 Dead, many infected police officers have tonfas hanging from their belts, though they can not be picked up upon their death.