Call of Duty: Ghosts
Takedown is an excellent complement to any stealth-based class build. Experienced players often pay attention to the skull-marks, as it indicates that the player is potentially close to enemy fire or an enemy player, and gives them time to seek cover. Takedown eliminates such advantages from enemies, and allows the player to dispatch an enemy without alerting his/her teammates, especially so when used with a Silencer or Knife and the Off The Grid perk.
The perk is most useful when flanking enemy positions, as it allows the player to pick off enemies one by one before they notice that their perimeter has been breached. It's usefulness with Sniper Rifles, however, depends on the player's style. When using a suppressed sniper, it can be used to lure enemies into open areas, as the lack of skull-marks may lead them to believe that the area is clear. When using an unsuppressed sniper, it may not be as useful as you will show up on the minimap anyway, and enemy players will correspondingly avoid areas where they may be picked off by a sniper.
Call of Duty Online
Takedown returns in Call of Duty Online as a Tier 1 perk. Like in Call of Duty: Ghosts, its user can kill enemies without leaving a skull-mark on the enemy HUD. It also makes users immune to Counter-UAVs and makes enemy footsteps louder. Users of this perk can hear enemies equipped with Ninja since Ninja only makes footsteps quieter instead of silent.