Complete the following tasks to unlock the corresponding effect.

Unlock 3 Bonus Missions:
Successfully beat the 1st 15 missions on any difficulty setting except Initiate.

Unlock Cheat Menu:
On Graduate setting beat the first 15 missions then go to 'Start Game' to activate the cheat menu to be able to unlock unlimited health and ammo and also Mission Select.

Enter Locked Doors without finding the Switch:
When you reach a gate or door that requires a switch to be deactivated before you enter, press and hold L, R, Select and B for 2 seconds and if you have entered the code correctly you will hear a voice in the background say 'Trust No One' and the colour of the screen will turn black and white for a second. After this has happened you can now enter.