Cease-fire
From Halopedia, the Halo wiki
The act of ceasing fire was introduced in the first Halo game. This allowed gamers who were involved in making movies or Machinima able to act as if they were in a holstering position.
Halo:Combat Evolved
Firstly introduced in the game, the concept of ceasing fire was not taken as it were no use. When Red vs Blue series came online in the internet, it is widely accepted for gamers who started making videos. Within the game, this can be done by moving the viewpoint downwards. Although the user is facing to the ground, other players will see the user in a normal position.
In Halo:Combat Evolved, using a M6D Pistol or a Plasma Pistol would make a nicer appearance.
Halo 2
Seeing that Red vs Blue helped in the Halo franchise, Bungie added a neat feature where the player could simply cease fire or holster their weapon by just tapping down the D-Pad. This feature boost Machinima production skyrocket.
In Halo 2, not all weapons can be holstered such as dual-wield weapons, rockets and swords
Halo 3
In Halo 3, the feature is still within the game but rather in a button combination. The player can cease fire or holster in Halo 3 by pressing LeftButton+RightButton+A+LS+D-PAD DOWN all together at the same time. Keep holding the combinations together for 3 seconds and the weapon at you HUD will disappear. This feature would not allow support weapons, dual-wield weapons, and swords to be holstered.
The player would not be able to see his/her weapon holstered but other players would. This feature was first used in public by Red vs Blue members.
