In Raid on Area 51 you are the lone security officer in charge of stopping over a million UFO enthusiasts from entering the compound.

Shoot anyone coming in through the gates in an attempt at keeping them from finding our alien secrets. Use standard human weapons as well as a few pieces of reverse engineered alien technology to keep the hordes from getting inside the base. Don't let your gun overheat or else you'll have to wait for it to cool down and lose precious time. Each civilian that enters the base increases the chances for the release of top secret, alien info.