Here is a complete cheat and unlockables list for the Xbox360 version of Mortal Kombat: Armageddon.

Codes performed at the "?" box, inside the Krypt:
Nitara's alternate costume - Down, R, Up, R, R, Right
Drahmin's alternate costume - White, Right, A, White, Up, Up
Frost's alternate costume - Down, White, R, R, B, White
Shang Tsung's alternate costume - R, Left, Up, B, Up, White
Red Dawn arena - B, R, Up, X, B, Down
Shinnok's Spire arena - Left, Left, B, Up, Y, R
Artika Arena - Beat all 7 trials in Artika Obliesk
Pyramid of Argus Arena - Collect 40 Relics in Konquest Mode or R, R, X, A, White, Up
Falling Cliffs arena - White, B, X, A, B, Y
General Reiko's Map Room arena - White, Y, R, Up, A, A
Nethership Interior arena - R, Left, Left, Down, R, X
Mortal Kombat - Armageddon promo movie - Up, Up, Down, Up, L1, X
Motor gameplay movie - Y, Up, White, R, R, White
Armory music - A, X, Left, Y, X, A
Lin Kuei Palace music - White, Left, B, A, White, Right
Pyramid of Argus music - Down, Left, White, White, Up, R
Tekunin Warship music - Up, B, R, R, R, A
Pyramid Of Argus concept art - A, R, R, White, Up, Up
Pyramid Of Argus concept art - Y, Left, Left, A, Down, B
Blaze concept art - R, Y, White, White, R, X
Early Taven concept art - Up, A, White, Down, White, A
Firewall arena concept art - Up, X, R, White, B, R
Ed Boon concept art - R, Left, Up, B, White, R
Mileena's car design concept art - White, Right, Up, R, Y, Up
Sektor's Pulse Blade concept art - White, R, Left, A, Up, R
Unused Konquest Trap concept art - B, White, Y, Down, B, Left

Kreate-A-Kharacter Unlockables:
Elder Gods Female Armor - Belt Inside a golden chest in a locked gate in Arctika after the second obelisk which opens after you defeat the Tengu Ninjas
Elder Gods Female Armor - Cape Inside a golden chest which is in the area after you meet and defeat Sonya
Elder Gods Male Armor - Belt Inside of a golden chest to the right after you open the first door in the Tekunin
Elder Gods Male Armor - Glove Inside of a golden chest after the second fallen log and to the right in Botan Jungle

Soundtracks are found in Konquest Mode, in the shape of musical notes:
Bo'Rai Cho's Brewery Tune - It's located after the bridge and in the cave to the right in the Botan Jungle
Botan Jungle Track Tune - Get the musical note which is located to the left before the second fallen log in Botan Jungle
Lumber mill Fight Tune - Get the musical note after the second crusher when you return to Arctika after the second obelisk
Subway Fight Tune - Get the musical note after you defeat Sonya Blade in Arctika
Tekunin Warship Tune - Get the musical note in the area where you get attacked by Black Dragon Thug's in the Botan Jungle

Unlock Arenas:
Artika Arena Beat all 7 trials in Artika Obliesk
Pyramid of Argus Arena - Collect 40 Relics in Konquest Mode
The Krypt - Collect 60 Relics in Konquest Mode

Unlock Characters:
Unlock Blaze - Collect 50 Relic items in Konquest Mode
Unlock Daegon - Collect 30 Relic items in Konquest Mode
Unlock Meat - Collect 10 Relic items in Konquest Mode
Unlock Taven - Complete Konquest Mode
Unlock Meat - Up, X, X, B, B, Up
Unlock Daegon - or R, R, Y, Down, Down, X
Unlock Blaze - Y, X, Left, R, Left, B
Unlock Taven - R, Left, White, Up, B, Down

New costumes:
Ashrah's Alternate Costume - Defeat the Ice Beast you encounter in Arctika and open the chest that appears
Baraka's Alternate Costume - Kill all of the enemies in the final room of the Tekunin Warship and open the chest
Cyrax's Alternate Costume - Kill all of the enemies in the third room of the Tekunin Warship and open the chest
Ermac's Alternate Costume - Found in a chest by the left wall in the room where you get attacked by the Red Commandos
Hotaru's Alternate Costume - In a chest close to the wall in the second room of the Tekunin Warship
Hsu Hao's Alternate Costume - In a chest on the right walkway after you wake up on the Tekunin Warship
Jax's Alternate Costume - Once you enter Arctika turn around and go to the left to find an invisible chest
Johnny Cage's Alternate Costume - Defeat the Tengu Guards at the beginning of Arctika and open the chest that appears
Kano's Alternate Costume - In an invisible chest to the left as you enter the last room of the Temple of Argus
Kira's Alternate Costume - Step on the second Giant Spider in Botan Jungle and open the chest that appears
Kobra's Alternate Costume - In an invisible chest behind the first monoth in the Botan Jungle
Kung Lao's Alternate Costume - Found in a chest to the right after you enter the Temple of Argus