Here are some codes that will make the game a lot easier, all you have to do is go to the 'Options' menu and then 'Cheats' and enter the code for the effect you want in the game.

Hide the Beat Marker:
Enter the code 56239

Show ALL Moves in the Movelist (Livin' Da life and Jam Mode):
Enter the code 43649

HUD Turned Off in Battles (you won't be able to see the song track or move you're doing):
Enter the code 41549

Unlock ALL Jam Mode Levels:
Enter the code 92750

Unlock ALL Jam Mode Music:
Enter the code 85872

Unlock ALL Jam Mode Characters (includes Crazy Leggs):
Enter the code 85363

You are put at Club Level in Livin' Da Life Mode:
Enter the code 17345

You are put at Pro Level in Livin' Da Life Mode:
Enter the code 11910

Unlock ALL Livin' Da Life Mode Clothes:
Enter the code 20014

Unlock Livin' Da Life Mode 5* Level Moves:
Enter the code 50361

Unlock ALL Livin' Da Life Mode Music:
Enter the code 78727

Unlock Crazy Legs:
Enter the code 93665

Unlock Everything in Livin' Da life Mode (Clothes, Music and Moves including 5* Level):
Enter the code 39572

Unlock Everything in Jam Mode (Characters, Levels and Music):
Enter the code 34589

Unlock Red Bull King of The Ring:
Enter the code 83083

Always have Maxium Hype (opponent also gets it):
Enter the code 15483

Clear ALL the Cheats:
Enter the code 26939

This is achieved when you have completed the battle on any difficulty setting with Kmel.