The Garrote Wire is a weapon used by Alex Mason in Call of Duty: Black Ops to silently kill a Tropas guard trying to alert Fidel Castro's base of the invasion of the Op 40 in the campaign mission "Operation 40." It is used to strangle the guard while providing a silent and clean death.
In WMD, it's used by Jason Hudson. If the player is undetected, and kills all the guards except for the one guarding the door, run down to him, undetected, and melee him. Sometimes Hudson knifes him to death instead by strangling him.