Enter these codes at the Enigma Machine.

Code - Result:
EAGLE - Unlock Mission 2, A Storm in the Port
HAWK - Unlock Mission 3, Needle in a Haystack
PARROT - Unlock Mission 4, Several Bridges Too Far
DOVE - Unlock Mission 5, Rolling Thunder
TOUCAN - Unlock Mission 6, The Horten's Nest
SEAGULL - Get a Gold Medal on the current mission
SILVERSHOT - Silver bullet, One hit kills enemies
BOUNCE - Rubber grenades
HIDENSEEK - Invisible Enemies
SUPERSHOT - Snipe-O-Rama, all weapons are sniper mode
HEADSUP - Achilles' head, Enemies only dies of headshot