Harpoon

A harpoon is used in the mission "Vorkuta" to take down an enemy Mi-8 helicopter. Mason wields a KS-23 which shoots a harpoon attached to a rope on a roof and shoots the helicopter with it. The helicopter then crashes due to the rope preventing it moving. This was step 5 of the escape plan - "Skewer the winged beast".

Trivia

 * If the player misses the helicopter with the harpoon, they are unable to enter the building to escape, meaning the player will be killed by the helicopter. Reznov will also yell "No! Mason!", which is odd, because all other deaths in game are never recognized by NPC, they just continue the mission and/or diologe.
 * It is actrualy a KS-23.