Unlockables
On the chapter selection screen, hold the "Select" button, and then press "Right," "Right," "Left," "Left," "Square," "Square." This code unlocks all the levels and bonus content.
By completing "Call of Duty 3," you will unlock a series of interviews. Available interviews come from veterans Gordon Boulton, Sgt. John D. "Bud" Hawk, and Sgt. Stan Markut.
"Night Drop" Mission Shortcut
After you encounter the French rebels in the "Night Drop" mission, you can either go left to the Flak 88s or to a house at your right. Head to the left, eliminate the Nazis around the gun and in the ditch, and destroy the rest of the Flak 88s. You'll encounter the house from the beginning of the mission. Eliminate all the enemies in the house, and then fall through the burning floor to find your allies waiting there.
Moving Friendlies
If a friendly character is blocking an area you need to access, you can use your gun to make him move. There's no risk in harming him, since you can't shoot friendlies. Using ADS, aim at the friendly and press the fire button. He should move away from your intended destination.
Scoped FG42 Locations
The fully automatic scoped FG42 features increased range and accuracy over its counterparts. This rare weapon only appears during two missions in the game. In the mission "The Island," you can obtain a scoped FG42 from a man beneath the second bridge. During the trench-defense portion of "The Mace," you'll find one by ignoring the men's advice and following the path to the right. The scoped FG42 will be leaning against a crate.