Gravity rifle
From Halopedia, the Halo wiki
The Gravity Rifle was going to be the covenant sniper of Halo: Combat Evolved. Bungie decided to delete this weapon much like they deleted the engineer. They do have the model in game but they never made a proper texture, first person model, and projectile.
Template:Deletemat (Indeed the tag is customized for Halo 2's Deleted material, but you get the point.)