The Guardians
From Halopedia, the Halo wiki
Summary
In both Halo 1 and Halo 2, when a player in multiplayer is killed inexplicably (ie by a physics glitch or by the environment), the message reads "_player_ was killed by The Guardians". There are also ways to do this among players (guardian glitch). For example, aim at a teammate's head with a battle rifle (or a pistol or carbine) other weapon, right trigger and Y simultaneously until he dies. Another way is when a player is killed by a melee attack from another player who died just as they did the melee attack.
Notes
- If you do this right, it should show the weapon firing, come down, then immediately fire again without seeing the secondary weapon.
- Shields and friendly fire must be off to do a guardian glitch on your teammate.
- Doing this while moving will result in you dying instead of your teammate.