Splinter Cell: Chaos Theory cheats and cheat codes for Gamecube

Unlock elite Mode
Finish the Story Mode to unlock Elite Mode, where you only have a 
knife to use.

Unlock movie trailer:
Finish the Lighthouse mission in single mode

Unlock all co-op missions:
Hold L + R at the main menu and hit X(5 times), Y(5 times). 
A sound will confirm correct code entry.

Unlock all regular missions:
After signing into your profile, on the menu screen 
hold L + R and press X(5 times), Y(5 times). 
A sound will confirm correct code entry.

Keypad codes:

Mission 3: Bank
Keypad before president's office: 3490
Keypad to bank's back door: 3901
Keypad to left security booth on 1st floor: 3624
Keypad to main security room: 2306
Keypad to right security booth on 1st floor: 3624
Keypad to safe in president's office: unknown
Keypad to treasurer's office: 8645

Mission 4: Penthouse
Keypad To Dvorak Room: 0280 

Mission 5: Displace
Keypad to central server room: Code 2109
Keypad to CEO's meeting room: 2346
Keypad to CEO's office: 2609
Keypad to door between meeting room and lobby on 1st floor: 8136
Keypad to door between meeting room and lobby on 2nd floor: 8136
Keypad to fire escape: 3485
Keypad to R&D server room: 9205 

Mission 7: Battery
Keypad to shipping area: 1879
Keypad to elevator: unknown

Mission 9: Bathhouse
Keypad to owner's office: 3650 
Mission 10: Kokubo Sosho