Cut Halo 2 weapons
From Halopedia, the Halo wiki
A Covenant counterpart to the UNSC Flamethrower, the Disintegrator is featured in the Halo 2 Beta and can be spawned via modding. The weapons is untextured and fires flame-like particle effects - though in third-person the effects are more akin to a kind of red plasma. The weapon appears to have a cooldown bar of some kind around the reticule, though this is nonfunctional in the beta.
General-purpose machine gun (GPMG)
Although the M247 machine gun is featured in-game as a a support weapon, the general purpose machine gun (GPMG) was seemingly intended to also be available for use as a weapon in first-person. In the launch build of Halo 2, strings in the game files referenced the GPMG such as picking up and switching to the weapon. The weapon was not seen physically until the release of Halo 2 on PC as part of Halo: The Master Chief Collection, when the GPMG was added to the game's shared directory, allowing it to be spawned in and used via modding.
The GPMG is complete with firing, reload and melee animations, sound effects and firing particle effects, and features an altered model including a removable magazine and a buttstock not found on the original machine gun model.
Machine gun turret with grenade launcher
In early concept art and builds of Halo 2, the M247 machine gun was attached with an over-barrel 25mm grenade launcher.
At one point in the development of Halo 2, the Suppressed SMG was intended for inclusion. The weapon features unique firing sound effects and particle effects alongside a suppressor on the barrel, though otherwise appears to inherit all the properties of the basic M7 SMG. The M7S would later make its in-game debut in Halo 2 for Windows Vista as a weapon spawn on the map Example, before being prominently featured in Halo 3: ODST. The later release of Halo 2: Anniversary would see the Suppressed SMG included in the game's updated multiplayer component.
The release of Halo 2 on PC in The Master Chief Collection similarly added the Suppressed SMG to the game files, allowing it to be used through the use of modding.