Halo 2 was the first Halo game to feature dual-wielding weapons.
The feature allowed players to carry and fire two compatible one-handed weapons at the same time. It changed combat by increasing short-range firepower and letting players combine weapon types, although dual-wielding also prevented the use of grenades and limited some other actions.
Halo 2 introduced the mechanic as part of its broader expansion of the original game’s combat system. It also added new weapons, playable Covenant missions, online Xbox Live multiplayer, and a more elaborate story structure.
Halo 3 retained dual-wielding but adjusted the weapon roster and combat balance. Later games moved away from the mechanic, so players who remember it from Halo 3 may incorrectly identify that game as its introduction. The feature first appeared in Halo 2.