The Magnum, (M6 series) is a weapon in all of the Halo games. It's commonly used to "represent" the characters talking to one another in the series.
In scenes filmed in Halo: Combat Evolved, characters are usually shown wielding the Magnum as the gun lowering technique known as "Alert carry". Any other weapon would look too aggressive in passive situations. With Machinima in mind, the programmers of Halo 2 decided to implement gun lowering into the game, allowing the characters to be holding most weapons without looking too aggressive.
In scenes filmed in other games, the Magnum is most often the secondary weapon of many characters, but is the main weapon of Sister, Carolina, and C.T. It is also commonly used in scenes in which characters are not supposed to wield weapons such as when being disarmed or taken hostage, which is referred to when Sarge tries to hold onto his pistol when Washington orders him to drop his weapons. The Magnum is a standard issue weapon for Red and Blue armies. It is also used by members of Project Freelancer. One of the project's training battles included the use of Magnums, with paralyzing paint loaded into them.
- Sarge's statement about the magnum being not as "effective as they used to be," in Upon Further Review is a real life reference to when the magnum was considered overpowered in Halo: Combat Evolved which was weakened in future games to "balance" the gameplay.
- The only other weapon in Halo: Combat Evolved that achieves the same "idle pose" is the Covenant Plasma Pistol, which was repurposed into a Medical Scanner within the Red vs Blue universe.
- Rooster Teeth always uses the Magnum sound effects from Halo: Combat Evolved regardless of which game engine footage is being shot in.