Battle Rifle-Plasma Rifle
From Halopedia, the Halo wiki
During the cutscene Uncomfortable Silence where the Arbiter is attacked by an Enforcer and is saved by a Phantom, the phantom never really shoots. Instead there is a combined weapon that shoots the Enforcer, as seen in this image. You can't see it in the Cutscene only when you pause the game and move the camera angle as shown in the below video link
