This is already a known quantity to the PlayStation crowd that's had the Resident Evil series for a while, but for Xbox 360 newcomers:
Resident Evil 5 has an unlockable mini-game called The Mercenaries. In The Mercenaries, you'll participate in modified levels from the story mode, but this time ammo will grow increasingly scarce while the enemy spawn rates will grow increasingly robust. The bad guys will get nastier and nastier during the timed challenges.
