Gravity wrench
From Halopedia, the Halo wiki
The Gravity Wrench was a deleted Covenant weapon intended for an early version of Halo: Combat Evolved. It may have also inspired the Plasma Pistol, as the weapon must first be charged, and then will fire a strong ball of energy. In addition to that, it appears to act like an early version of the Flamethrower, or other Support Weapons.