Pause game play, then hold L + R and press B(2), Left, Y, B, A. The phrase "Enter Cheat" will appear to confirm correct code entry. The following codes can now be enabled.
Enable the "Cheat mode" code, then press A, Y, B, Right, Y, B. Note: This code only works in single player mode.
Enable the "Cheat mode" code, then press B, Down, B, Up, Y, B.
Enable the "Cheat mode" code, then press Down, White, L, Up, X. The person you have to hunt down in various missions will be killed.
Pickup OSS document:
Enable the "Cheat mode" code, then press Up, A, Black, R, Up, X.
Enable the "Cheat mode" code, then press White, R, White, L, Y(2).
You will receive a free medkit at the end of every level for each surviving member of your squad.
You will earn one revive at the end of a mission for completing all mission objectives.
When your on the last level of the first attacks and the Panzer comes through the wall, let it blow up the mini houses. When they are blown up, get the grenades in them. If you get enough of them, you can blow up the Panzer. Keep throwing the grenades; it takes awhile.
Defeating the Nemesis Bosses:
Before you get to the Bosses, fill up your adrenaline meter. This can be easily done by shooting head shots. Once your meter is full, save it until you get to the Boss. Once you see him, press Up. You will now have limited immortality and unlimited ammunition. If you have a sniper rifle, you can shoot the Boss in the head a few times. If you have a sub-machine gun such as a Thompson or an STG-44, you can run up to the Nemesis and shoot him. Another way to inflict serious damage is to use a rocket launcher. Note that you will not have unlimited ammunition for this -- it is best to have a good back-up weapon. If you still have not killed him and your meter is almost empty, retreat to some cover. Note: If there are enemies surrounding the Boss, which is true in most circumstances, eliminate them before you attack the Boss or you will be slaughtered once your meter is empty.