To enable secret functions, hold R+L and then use the following combinations:
All Psi powers: B(2), Y, White, Left Analog-stick, Y
Full lives: Left Analog-stick, White(2), B, A, Right Analog-stick
Full ammunition: Right Analog-stick, A, Left Analog-stick(2), Y, B
All items: Right Analog-stick, B, White(2), Left Analog-stick, Y
Maximum rank and all Psi powers: Left Analog-stick, Right Analog-stick, Left Analog-stick, White, B, White
Invincibility: B, White, B(2), Y, Black
Full Arrowheads: A, Right Analog-stick(2), White, Y, X
New text: White, A, Left Analog-stick, White(2), B