Successfully complete the game under the easy difficulty setting to unlock the "Big Head", "Ricochet", "Head Shot", and "Ricochet All" cheat options. The remaining cheat options can be unlocked by completing the game under the other difficulty settings.
Russian campaign
On the first tank level in the Russian campaign, it is best to use first person view to shoot the Nazis that have Panzershrecks and MP-40s. The MP-40s cannot hurt you, but are annoying. If you use third person view, you will miss.
Teddy Bear
In the stage Surrender at Aachen (Western Front), you will be in an enemy occupied house right from the start. The small room directly across from where you start from has a small teddy bear you may acquire with no known effect.
All Levels
At the level select screen hold Up on controller two and on controller one press Start, Select, Select, Square.