the tactical knife ingame
The Tactical Knife can be picked up in the level memorial in the first house with the guard in it. It can be thrown at an enemy for a silent kill but then you need to run over to it and grab it again to keep using it. It also increases the power of your melee attack. In multiplayer you can throw an infinite amount of the one hit kill knives.
The Tactical Knife is similar to the throwing knife from the original GoldenEye 007.