Combat knife

The Combat Knife, occasionally referred to as the Close Quarters Combat Weapon System in technical manuals, is a multi-purpose infantry-sized knife used by the United Nations Space Command.

Overview
The multi-purpose combat knife has a 20 centimeter (7.9 inches) blade made of high carbon steel, an anti-flash coating, edge coated for corrosion resistance and is 43.3 centimeters (1.42 feet) when sheathed. All UNSC troops are issued with a combat knife for close quarters combat or in situations when ammo is scarce. It can also be used around campsites when needed. It is also balanced for throwing. It appears in the novels and on the backs of Orbital Drop Shock Troopers in Halo 2 and Halo 3, and in The Babysitter, but not Halo: Combat Evolved. One was used in cutscenes in Halo Wars, and another was used in cutscenes in Halo 3: ODST. The combat knife will finally play an active role in gameplay in Halo: Reach, where it will be used for special stealth kills.

History
Knives have been used in battle almost since the dawn of warfare, first as a sharp piece of rock, and then metal proved effective during a period of time where projectile weapons were not readily available. The combat knife later branched off and became a sword, while others used daggers. For thousands of years, knives and swords have been a weapon of choice for soldiers. Even after the invention of the firearm, knives were still used as bayonets for close-quarters-combat. Sabers were still issued in World War I. As war tactics shifted from trench warfare to attrition warfare, knives became last-resort weapons or simple tools. By 2553, the UNSC still uses knives, showing that such an easily accessible and created weapon still runs strong even thousands of years later. Even the Covenant (especially Brutes) uses variants of the basic knife.

Appearance
One of the few times a combat knife can be seen in game is on the lower backs of ODSTs or on the left chest of the CQB chest plate armor permutation, though they are never used in combat. In Halo Wars, Sergeant Forge used a combat knife which he named "Lucy" to wound the Arbiter and kill him with his own energy sword. It also has a serrated edge like other combat knives as mentioned in Halo: The Fall of Reach. Gunnery Sergeant Buck used a combat knife to wound, and subsequently kill, a Brute Chieftain, afterwards casually flicking the alien's blood off of its blade.

Trivia

 * The ODST Action Figure, made by Joyride Studios, has a Combat Knife that can be held by the action figure's hand.
 * It was Frederic-104's trademark weapon, after the MA5B Assault Rifle.
 * In Halo 3 Concept Art for EGM, a Spartan-II is shown with a Combat Knife on his/her right leg, however this was just an artistic look for the ODST armor.
 * A larger version of the combat knife, called the Machete, was intended to be used in the early Halo: Combat Evolved build, but was cut before it made it into the final game, replaced with the game's use of melee attacks from any weapon.
 * The Spartan CQB chest permutation in Halo 3 multiplayer has a combat knife and its holster attached to the left chest section. It cannot be drawn or used, and is purely ornamental.
 * In Halo Wars, Sergeant John Forge has a combat knife named "Lucy", which he used to wound the Arbiter before killing him with an Energy sword.
 * In Halo 3: ODST, the character Buck can be seen wearing a combat knife on his chest plate, which he uses to kill a Brute Chieftain by stabbing him in the neck.
 * In the Halo: Reach world premiere cinematic, Emile-A239 is sharpening a combat knife using his shoulder plate. It has been confirmed that knives will be usable in-game to perform special stealth kills from front and behind.
 * In the Halo Legends episode The Package, Frederic-104 uses a combat knife distinctly different than previous incarnations. The blade itself is similar in terms of shape, but the handle has three circular holes cut out of it, most likely to reduce overall weight. Also the back edge is serrated. It should also be noted that they are stored in the shoulder pauldrons of his MJOLNIR Powered Assault Armor/Mark IV.