Cheat Mode
At the main menu push Up, Up, Down, Down, Right, Right, then press start and hold L + R at arcade.
Submitted by Sammie.
Goro Code
When choosing your character highlight the hidden panel, then hold the left and right triggers down and press up, left while still holding the triggers. This gives you Goro as a playable character.
Submitted by Jimmy_G.
Noob Saibot Code
On the character selection screen highlight the hidden panel, then press and hold the Left and Right triggers, while still holding the triggers press Up, Up, Left, Left, Left, Left, A button. This will make Noob a playable character.
Submitted by Jimmy_G.
Play as Sector
At the character select screen, go to hidden, then press and hold L + R while on hidden. Next, move the cursor to Cyrax (while holding L + R) and select Cyrax with the 'A' button.
Submitted by Dan_Hall.