Ice Nine - Cheat mode

Bonus missions:
Complete the first fifteen missions under a difficulty setting greater than "Initiate" to unlock three bonus missions.

Cheat menu unlimited health and ammo, mission select:
Beat 1st 15 missions on Graduate. Go to "Start Game" to activate cheat menu and play any mission with cheats.

Open doors:
When reaching a door or gate that requires a switch to open, hold L R Select until the screen flashes the phrase "Trust no one" is spoken.

Veteran difficulty:
Complete the first fifteen missions under the "Graduate" difficulty setting