Kao The Kangaroo Codes -

Level select:
Pause game play and display the map. Then hold L + R and press Up, Down, Right, Left, Up, X.

Unlimited lives:
Pause game play and display the map. Then hold L + R and press Down, Left, B, Left, B(2).

Unlimited energy:
Pause game play and display the map. Then hold L + R and press Down, B(2), A, Up, Left, Right.

Unlimited gloves:
Pause game play and display the map. Then hold L + R and press Down, Right, Up, Right, Left, B.