Dual wielding
From Halopedia, the Halo wiki
Summary
Dual wielding is a feature found in Halo 2 that allows you to wield two weapons at once, effectively doubling your firepower at the expense of meleeing/throwing grenades. One of the best ways to dual wield is the SMG/Plasma Rifle/Plasma Pistol combo (also known as the newb combo) which allows you to take down your opponent's shields with the energy of Plasma and then use the aptly named "bullet hose" to rip through the flesh of your opponents very quickly.
A bug happens in multiplayer when a player has a weapon in is backpack and dual-wields two of the same weapons. Three sets of shots come out of the player. If needlers are used, then the third needle stream comes from the player's head.
Advantages/Disadvantages
Advantages
When a player is dual-wielding, he or she is able to put many more projectiles in the air than if he hadn't been, causing more damage and eliminating targets faster than if he had only been using one weapon.
Plasma weapons can be combined with human weapons, easily taking down the shields then finishing off the target.
Disadvantages
When a player is dual-wielding he/she is unable to use grenades (unless they are using the "Boxer" control setting).
When a player must reload his weapons, or if his weapons overheat, he is very vulnerable.
You need to drop the duel weapon (left hand) to switch weapons.
