Triple wielding

Triple Wielding is a glitch interrupting with Halo 2's Dual Wielding system. As the name says, you wield three dual wieldable weapons at the same time. Though you don't shoot with them all, you do get 50% extra ammo, which can come very handy on big maps or on campaign maps with Flood or Hunters.

How to perform a triple wielding
1.Figure out which weapon you wish to triple wield(must be dual wieldable). This will be called weapon A. You will need another dual wieldable weapon, that is different from weapon A. This is weapon B.

2. To triple wield a weapon, first get two weapons(A and B). Pick up the first(weapon A), then press Y to switch weapons. The other weapon must be dual wieldable, but different from the one that will be triple wielded(weapon B).

3. Find another weapon A, and dual wield it, by holding Y, with weapon B. You should now have weapon A as a secondary weapon, and weapons A and B as primary weapons, dual wielded.

4. Now, trade weapon B for another weapon A, by using X.

5. You have successfully triple wielded.

There is also a second method. However, this method gives you three weapons to cycle through, instead of just extra ammo. To do it...

1. Make sure you have at least one dual-wieldable weapon. For this example, let's say we have a Needler and a Battle Rifle.

2. Stand over another dual-wieldable weapon, such as a Plasma Pistol.

3. With the needler out, throw a grenade and while your arm is in the action, hold Y.

4. If you aren't host, it should say Picked up a Plasma Pistol, but you won't have actually picked it up (if you are host, you can't do it). As soon as you see that, tap Y repeatedly.

5. You will now be able to cycle through Needler, Plasma Pistol and Battle Rifle. To the host, you will just look as if you were dual-wielding a needler and plasma pistol.

On YouTube, there is a video guide that might be more helpful than what I just wrote, it can be found here

There is also a third method in which gives you three weapons and can be used anywhere by any alien dual wielding weapon.

1. Have two similar weapons dual wielded, and look straight down.

2. Melee the ground and then quickly pick up the weapon, the corner of your screen should say you picked up the weapon, do this three times or until the screen says you have picked up the weapon three times. You're done.

With plasma rifles and needlers the rate of fire should increase while the overheating decreases.

Trivia
A form of triple wielding (where the player holds two of the same weapons) can also be done in Halo 3, in almost the exact same way.