Only found in multiplayer, it is available if the player removes a primary and/or secondary weapon, which is then replaced by Combat Knife in-game. In addition, planting an Assault Shield will leave the player with their other weapon (if they had one) and a Combat Knife. Therefore, a Combat Knife does not cost an Allocation Point in Create-a-Class.
Compared to the standard knife, it features a faster melee speed and a small amount of lunge. It is held in the right hand, as opposed to the standard being held in the left. The player also does not grunt when knifing, unlike with the standard. Lastly, equipping the Combat Knife grants a 50% increase in sprint duration. Another unique feature is that while the Combat Knife is equipped, pressing the fire button will use the knife. It should also be noted that the combat knife cannot be used to destroy ground scorestreaks such as the Sentry Gun and Guardian.
The challenges for the camouflages are:
DEVGRU - Get 10 kills with the Combat Knife (knife is held instead of a weapon).
A-TACS AU - Get 20 kills with the Combat Knife (knife is held instead of a weapon).
ERDL - Get 40 kills with the Combat Knife (knife is held instead of a weapon).
Siberia - Get 60 kills with Combat Knife (knife is held instead of a weapon).
Choco - Get 80 kills with the Combat Knife (knife is held instead of a weapon).
Blue Tiger - Get 100 kills with the Combat Knife (knife is held instead of a weapon).
Bloodshot - Get 120 kills with the Combat Knife (knife is held instead of a weapon).
Ghostex: Delta 6 - Get 160 kills with the Combat Knife (knife is held instead of a weapon).
Kryptek: Typhon - Get 200 kills with the Combat Knife (knife is held instead of a weapon).
"Standard issue military knife for CQC. Fast, quiet and deadly."
The Combat Knife reappears in Call of Duty: Ghosts. Equipping the Combat Knife grants a 75% increase in sprint duration. Just like in Black Ops II, the fire button will use the knife. Unlike in Black Ops II, the Combat Knife can be selected like other weapons in the Create-A-Class directly. In addition, it is automatically selected when the player clears their Primary Weapon in Create-A-Soldier. It can be picked up and dropped during gameplay, unlike back in Black Ops II. The Combat Knife is also found as the last weapon in Gun Game, where it is used with the Throwing Knife. Getting kills with the Combat Knife in Gun Game does not count towards their streak, and instead will simply act the same as a regular melee kill in Gun Game would. Equipping the Combat Knife in Multiplayer gives players an extra perk slot. The Combat Knife is the primary weapon of the Maniac gunstreak, alongside the Throwing Knife.
"Gold plated Combat Knife with Fast Melee. Unlocked at Prestige 5."
A patch on June 3rd, 2014 (June 4th, 2014 for some consoles) released a Gold Combat Knife. Players Prestige 5 will be able to access it immediately. It functions similarly like the Combat Knife from Call of Duty: Black Ops II, as it does not need to do the knifing animation. It is automatically unlocked in Private Match and Local Match along with the Gold PDW.
The Combat Knife returns as a weapon that can be used in the primary or secondary slot in Call of Duty: Advanced Warfare. There is no lunge on this iteration of the Combat Knife, making it considerably harder to use compared to its past incarnations. The knife drips blood after a kill (or paint instead if the player has Paintball Effects on).
To equip the Combat Knife in multiplayer, the player should simply remove their primary or secondary weapon depending on where they want it. In addition to it being able to be used that way, if the player crouches or goes prone in the Swimming Pool on the map Retreat or Terrace, they will not be able to use a gun, and a Combat Knife will be equipped instead.
The Combat Knife appears in Exo Survival, but only on the maps Retreat and Terrace by crouching or going prone in the pool like in multiplayer. Since most enemies will avoid going into the pool and can shoot at the player from outside of it, the Combat Knife has no real use, and it is unlikely the player will be able to get a kill with it.
The Combat Knife appears as the only special in Call of Duty: Black Ops III. Similarly to past games, it can be equipped in either primary or secondary weapon slots. Unlike past games, the Combat Knife has to be unlocked and equipped instead of being the default weapon given after removing either the primary or secondary weapons.
Although Diamond Camouflage is obtained by completing all camouflage unlocks for Specials, the "Weapons Mastery" challenge claims that the player needs to complete Mastery for every primary and secondary weapon.
The Black Ops II logo is visible on the Combat Knife.