The Elite Plasma Rifle Glitch is a glitch that appears near the beginning of the level The Package, in the gameHalo: Reach.
At the start of the level, go into the water. Jump onto the building to the far right, and go up the stairs. There should be about seven Special Operations Unggoy and one Sangheili General. Melee the elite to take out his shields and then shoot him. Instead of roaring, the elite should jam his Plasma Rifle into his mouth, and die shortly afterwards.