Day Of Infamy: Unlimited ammo
This trick requires the entrenching tool from the Search For Yamashita's Gold mission. As you are making your way up through the ship you will see a soldier that has been sprayed in the face with steam from an exploded pipe. Approach the soldier and press X. The message "Entrenchment Tool Used" will appear. This will unlock the "Unlimited Ammo" cheat in the bonus menu.