No weapon glitch
From Halopedia, the Halo wiki
The No Weapon Glitch is a glitch done in both Halo 1, Halo 2 & Halo 3 that removes the player's weapon.
Halo 1: Multiplayer
The No Weapon Glitch is not as well known in Multiplayer. But the process is pretty simple. It works easily on Halo: PC but is harder on xbox because there is less lag. It cannot be viewed by the person who has no weapon. There are two kinds of No Weapon Glitches in Halo PC, one from the hosts perspective and one from the clients perspective.
Walkthrough
To perform the glitch in multiplayer, you need have at least one other player to work with. Then, get multiple different Weapons together in a closed area, like in the Blood Gulch Base. Then, tap X (The button you have set for the "Drop Weapon" command) or E (The button you have set for the "Action" command) repeatedly over the weapons, this should make you continuously drop and pick up new weapons.
Eventually, you will not be able to drop your weapon. This is due to your weapon "phantoming." Now, all other players in the game will view you as if you had no weapon. Your partner should also have no weapon. However, if you were a client, the game will eventually automatically switch you to your other weapon. As a client, if you press tab, you can switch to your other weapon before this happens. You will discover either way after you switch weapons that you can't switch back to your other weapon, because your other weapon no longer exists.
Observations
If you observe a client who has no weapon, they will assume the animation for having no weapon, like in the pillar of autumn at the beginning of campaign. However, if you observe a host who has no weapon, they will look very different. The host assumes a phantom weapon stance. They are actually still holding their weapon, but you cannot see it. If they were holding, say, a sniper rifle when they lost their weapon. Their arms will look like they are holding a sniper rifle. They can still shoot and melee with their weapon, and if they switch weapons, you will see a weapon floating in the air where they switched. They can also switch out their "phantomed" weapon for other weapons, changing how they hold thier hands in the air.
Halo 1: Campaign
The No Weapon glitch on Halo 1 for the campaign is far more complicated. It involves Overloading the map with objects, such as Weapons, Grenades, and bodies, so that objects on the map start deconstructing. This is recommended to be done on the xbox version of halo, because with co-op, you can effectively overload the map. The way to overload the map is to continuously kill your teammate until the map starts to Overload. With a little luck, you will deload your weapons. You can also deload enemies weapons using this same method.
Halo 2
It requires an oddball and a plasma pistol to work in Halo 2. First, you would need the oddball, then charge your plasma pistol. Then, walk over the oddball and pick it up while still charging the pistol. If you did it correctly, you will have no weapon in your hand and have no reticule. However, if you come in contact with any weapon, you will automatically pick it up.
This can be used for some fun gametypes if everyone cooperates or can be used for making Machinima. Please note, however, players using the Spartan player model can still throw grenades while Elites can't when using this glitch, due to having no animation while not holding a weapon.
In addition this can be done in campaign. I would suggest Outskirts because the Blind skull can be grabbed on any difficulty or regret because the Assassins skull is always there;it just doesn't work on Heroic or lower. First do the glitch where you hold three of the same weapon with the plasma pistol. Drop your duel wielded one. Switch between your weapons to be sure that you have two plasma pistols. Then go to the level's skull. Do the trick as mentioned above but with both plasma pistols. You should now be holding no weapons, but with the abundance of weapons in campaign it will be very difficult to avoid weapons on the ground so I would carry the level's skull with you so you can redo the glitch.
Halo 3
This glitch can be achieved in Halo 3 as well. It mainly occurs in a custom game but occasionally will occur in Matchmaking, mostly during a Capture the flag game.
