Area 51

Unlocking Secret Tapes:
Scanning all five databank items in each stage yields one secret.
Completing the game yields one secret.

Upgrading The Alien Grenade:
In the stage Life or Death, there is a small key on a dead soldier
in one of the lifts where Cole starts the stage. Grab it to open
the small lockers in the stage. One of the small lockers in the
first power conduit pit has a databank item that upgrades the alien grenade.

 