Level Passwords
On the main menu got to quick start and input on of the following codes:

02 - 12B1S2Q22MQQ
03 - BJBBC3Q22VQQ
04 - BZBBC3Q22!RQ
05 - CJBCGQQ2FGRQ
06 - SZBCW5Q2F45Q
07 - TJVDKYQ2FW59
08 - TRVT6882F!W8

Level Passwords
On the main menu got to quick start and input on of the following codes:

02 - 12D1S2Q22MQQ
03 - BJDBC3Q22WQQ
04 - BZDBSMQZZ!QQ
05 - CJTCCQQ2FGSQ
06 - K2TK65Q2F4SQ
07 - T2TT68QGF!WQ
08 - 5JR5L1QGGGSQ
09 - 52T572Q4G4SQ
10 - VJVVLJQGGWSQ

All Levels Password
VZRFTMQ2G8SQ

Invincibility
At the title screen, press C-Right, then hold Z + B and quickly press R.

255 grenades
Change your weapon to the grenades and hold Z until the throw meter is filled. When the grenade is being thrown, hold Z again until the meter is full. Repeat this until you are on the last grenade. When it is thrown, you will have 255 grenades.

Flash bang grenade survival
To be unaffected by the flash bang grenades, turn on night vision goggles. Leave them on untill the effects of the grenade wear off.

How to kill tangos
Without being detected In Mission: Deep Magic

This (Believe or not) is very simple, all you have to do is bring grenades (Mission: Deep Magic) and you can kill everybody with them without being detected ;)

Team-mate picks lock
Use the following trick to make your teammate following you pick a lock. Quickly press Up, Right, Down and quickly move away. This does not always work the first time -- you may have to try again. If done correctly, you will see the teammate that is following you rubbing his hand on the door, and you will hear a lock picking sound.