These are some of the cheats I know that work and will unlock many things.
***WiFi info at bottom


G=Green
R=Red
Y=Yellow
B=B
O=Orange
P=Purple

CHEATS:
Always Use Slider:
G G R R Y R Y B

Flame Color:
G R G B R R Y B

Gem Color:
B R R G R G R Y

Star Color:
R R Y R B R R B

Line Six:
G R Y B R Y B G

AT&T Ballpark:
Y G R R G B R Y

Invisible Characters:
G R Y Y Y B B G

Auto Kick:
Y G R B B B B R

Hyperspeed:
G B R Y Y R G G

Air Instruments:
R R B Y G G G Y



CHARACTERS:
Aaron Steele:
B R Y Y Y Y Y G

Nick:
G R B G R B B G

Johnny Viper:
B R B B Y Y Y G

Rina:
B R G G Y Y Y G


CHEATS (continued)
*All Quick-Play Songs:
B B R G G B B Y

**Performance Mode:
Y Y B R B G R R


*Does not include downloadable content or custom songs.
**WARNING: You will not be able to see the notes using this mode.
***Codes may or may not work on WiFi.

Go to options and put these in to unlock the cheat:

Performance Mode
Press Yellow(2), Blue, Red, Blue, Green, Red(2).

Hyperspeed
Press Green, Blue, Red, Yellow(2), Red, Green(2).

Auto Kick
Press Yellow, Green, Red, Blue(4), Red.

Unlock Quickplay
Press Blue, Blue, Red, Green(2), Blue(2), Yellow.

Aaron
Press Blue, Red, Yellow(5), Green.

Nick
Press Green, Red, Blue, Green, Red, Blue, Blue, Green.

Johnny Viper
Press Blue, Red, Blue(2), Yellow(3), Green.

Rina
Press Blue, Red, Green, Green, Yellow(3), Green.

Air Instruments
Press Red(2), Blue, Yellow, Green(3), Yellow.

Invisible Characters
Press Green, Red, Yellow(3), Blue(2), Green.

AT&T Ballpark
Press Yellow, Green, Red(2), Green, Blue, Red, Yellow.

Gem Color
Press Blue, Red(2), Green, Red, Green, Red, Yellow.

Flame Color
Press Green, Red, Green, Blue, Red(2), Yellow, Blue.

Star Color
Press Red(2), Yellow, Red, Blue, Red(2), Blue.

Vocal Fireball
Press Red, Green(2), Yellow, Blue, Green, Yellow, Green.

Always Slide
Press Green(2), Red(2), Yellow, Red, Yellow, Blue.

Line 6
Press Green, Red, Yellow, Blue, Red, Yellow, Blue, Green.