Many different weapons - from statue busts to wrenches, knives and bricks - will pop up with the 'silent kill' prompt, but if there are enemies nearby, they'll still hear the impact and react accordingly. However, assumedly as a way to make the Fibre Wire still valuable in a game where you're free to strangle enemies with your bare hands, using it on an unsuspecting enemy will always be completely silent, no matter the distance to the next NPC. In addition, you can hold square/X to go straight into a dragging animation, making this the best way to thin the ranks of any area, providing you're sure you want to take someone out, rather than just knock them unconscious,
