Triple wielding
From Halopedia, the Halo wiki
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. Let's say that we want to triple wield three Needlers. First, have a Needler in your secondary weapon slot and a SMG (representing another dual wieldable weapon) in the first (in your hands).
2. Dual wield a Needler so that you end up having a needler in the left hand and a SMG in the right.
3. Now, trade the SMG for a Needler.
4. You have successfully triple wielded.
