Save those bullets, playa.
Recession is a skull in Halo: Combat Evolved Anniversary.
After being at the door Kig-Yar and Unggoy come running out of, being followed by Assault Rifle crossfire, keep to the left. At the left end of the area is a turret. Right behind that lies the skull, down the cliff.
Every weapon, Covenant and UNSC, use twice the amount of ammo they normally do. As such, players can run out of ammo very quickly and need to switch weapons often. This can form a difficult combination with Famine, where weapons don't drop with a lot of ammo to begin with, let alone use double ammo.