Karaoke Revolution Vol. 2 
  
PS2
  

Enter the following at the 'Press Start' screen:





All songs:


Square, Triangle, Down,
Left, Up, Right, L2, R2, Start 



All characters:


Up, Square, Right, Circle,
Square, Left, Circle, Up, L3,
R3

All costumes:


Up, Circle, Left, Square, Square,
Down, Circle, Right, R3, L3.

All venues:


Square, Triangle, Right,
Up, Left, Down, R2, L2, Start

GamePro T-shirt:


Down, R3, Up, R3,
L3, Down, L3, Up, Down, Square

Game Star T-shirt:


Up, R3, Right, R3, R3,
Left, R3, Down, Circle, Circle

Game Informer T-shirt for Angela:


Down, L3, L3, R3, R3,Circle,
Right, Square, L3, R3

Harmonix t-shirt for Ishani:


L3, Circle, Up, Circle,
Square, L3, Down, Down, R3

Konami T-shirt for Dwayne:


Right, R3, Right, R3,
Square, Right, Circle, Square, Down,
Left.
PSM T-shirt for DeVron:


  Left, Right, Left, L3,
R3, Down, Up, Up, Circle, Square


Enter the following  at the 'Cheat' screen:
Banana mic:


  L1, L1, R2, R2, Right, Down,
  Circle, Left, Up, Square

Toothbrush mic:


R1, L1, R2, L2, Right,
Left, Down, Up, Circle, Square

 Doll mic:


Circle, R2, Square, L1,
R1, L2, Square, Up, Circle,
Square 

Big head:


Down, Down, Down, Up, R1, L2,
R2, L1, Circle, Circle. 

Small head:


Right, Right, Up, Up, L2, L2,
R2, R1, L1

Big eye:


Square, Square, Square, Square, Circle, Down, Down,
R2, L2, R1

Glass character:


Square, Square, Circle, R2, R2, 
L2, Down, Right, Right, Up

Oil slick character:


L2, R2, L2, R2, Square,
Down, Circle, Up, Left, Right

Mercury character:


Circle, L1, R2, Up, Up, 
Left, Left, Square, Square, R1 

Wraith character:


R2, Left, R1, Right,
Up, Up, Square, Circle, Down, L2

Tough crowd:


Right, Up, Circle, Circle, Circle, R2,
R1, R1, L2, Down

Pirate crowd:


Square, Square, Left, Left, R2,
L1, R2, R1, Circle, L2

Robot crowd:


Circle, Circle,  Right, Right, R2,
R1, R1, R2, Circle, R2

Zombie crowd:


Left, L1, L2, Square, Square, L2, L2, L1, Left, Left. 


Thanks to Revolution readers Genius and dancefan!