Press A, Left, A, Right, A, Left, , A, Right repeatedly while playing as Ben.
Galactic Enforcer color set
Press Up, Right, Down, Left, A, B, Select at the level selection screen. A sound will confirm correct code entry. Go into any level and you will be in the "Galactic Enforcer" color set. Both Ben and all his alien forms will be black and white and official "Galactic Enforcers".
Gold Suit
On the main screen, insert the following password: A, B, X, Y, L, R, Select. Then, select a level as you normally would. This will unlock the Gold Suit for your use during the game, though you'll need to re-enter the password if you turn the game off and back on later.
Gwen 10 skin
Press Left, Right, Left, Right, L, R, Select at the level selection screen. A sound will confirm correct code entry.
Master Control
Successfully complete the game. Start a new session and collect all 30 Sumo Slammer cards. Enter any level under the "Insane" difficulty. The Master Control will be enabled, with unlimited Omnitrix battery, and the ability switch between aliens without reverting back to the human form.
Omnitrix aliens
Complete the indicated level below to unlock the corresponding Omnitrix alien.
Cannonbolt: Complete Hoover Dam.
Wildvine: Complete Seattle Space Needle.
XLR8: Complete Grand Canyon.
Skins
Enter the following codes at the 'Title' menu to unlock the corresponding skin. If you have entered the code correctly you will hear a confirmation sound.
Unlock Ultra Ben Skin
Press Up, Right, Down, Left, A, B, Select.
Upchuck
Press A, Left, Y, Right, X, Up, B, Down, Select.
Unlocks bonus mission
Press Left L Right R Up Down Select at the mission selection menu.
Upchuck
Press A, Left, Y, Right, X, Up, B, Down, Select at the level selection screen. A sound will confirm correct code entry. Upchuck will now be permanently unlocked; just select his silhouette on the Omnitrix.