Enter the following at the cheat screen.

Level select and full stats:
Up, Up, Down, Down, Left, Right, Left, Right, B, A, B, A.

All characters:
Down, Right, Right, Down, Left, Down, Left, Down, Right, Right, Right.

Super spin:
Left, Left, Left, Left, Right, Right, Right, Right, Left, Right, Left, Right, Up.

Regenerate Da Juice:
Left, Left, Right, Right, Left, Right, Down, Up, Up, Down, A, I.

Zero G Wallride:
Up, Down, Up, Down, Left, Right, Left, Right, A, B, A, B, S.

Perfect grinds:
B, I, G, U, P, Y, A, S, E, L, F.

Perfect manuals:
Q, U, E, Z, D, O, N, T, S, L, E, E, P.

Perfect handplants:
J, U, S, T, I, N, [Space], B, A, I, L, E, Y.

Infinite juice:
B, A, K, A, B, A, K, A.

Every key:
S, K, E, L, E, T, O, N.