Two Arbiters glitch

The Two Arbiters is a glitch that can be exploited on the Halo 3 level, Halo. The result of the execution of the glitch will be that you will find yourself accompanied by 2 Arbiters.

How To
The first step requires you to be able to kill the Arbiter right before you enter the room where the battle with 343 Guilty Spark is fought. In order to achieve this, you will have to do the Spartan Laser Glitch, and you should preferably play on Easy.

Once you have the infinite Spartan Laser, go to the door right before the fight with 343 Guilty Spark, but don't enter. Shoot the Arbiter with the Spartan Laser until he dies. Quickly after that, go through the door and initiate the cutscene. Once you finish the fight with 343 Guilty Spark, go outside and there will be 2 Arbiters. One standing looking at you and another already attacking the awaiting Flood. That one has the waypoint above his head. Once near the end of the hallway both Arbiters will stay back.

Explanation
This happens because when you enter the fight it originally unloads the Arbiters model then when finished with the fight it reloads him back to the hallway. But since you kill him the game registers him as not there so therefore not unloading him. And when you finish the fight he is still there and the game still loads the 2nd Arbiter because the game's code doesn't check if the 1st Arbiter is unloaded.