Infinite Weapons on Crow's Nest
From Halopedia, the Halo wiki
To receive Infinite Weapons on Crow's Nest you must do the following:
After Johnson tells you to go to the barracks, head back downstairs. You should get a checkpoint. Once you do, grab any weapon from one of the racks and take it to up to the upper level, then drop it. Go back down to the hall with the weapon racks. The weapon you took should have reappeared in the same spot on the same rack. The weapons will keep reappearing as long as one of them is removed. This is very useful, as you can get infinite -1 Battle Rifle or Pistol ammunition. This can be enormously helpful for the fight in the Motor Pool on higher difficulty levels, especially if you salvage the Plasma Pistols used by the Drones. This is most useful with the Famine Skull activated.