Killzone

Unlocks all levels:
Enter Shooterman for the name when creating a new profile
to unlock all the levels. You have to start a new
single-player campaign for this to work.

Shoot three shells with shotgun:
When using the shotgun, it has two modes of fire
(regular shoots one shell, alternate shoots two
shells). By pressing both fire buttons, you will shoot
three shells, which in most cases is more
useful. Try using this on groups or stronger enemies.

Play as Luger:
Successfully complete mission 2 in story mode.

Play as Hakha:
Successfully complete mission 4 in story mode.

Play as Rico:
Successfully complete mission 3 in story mode.

 