Lode Runner 3D
Pause the game. Now hold Z and press R, B, A, B, A, C-Up, C-Down, C-Left, C-Right,
C-Up, C-Down, C-Left, C-Right. You'll hear a sound to confirm, plus you'll see
an "Unlock Worlds" option.
Thanks to Revolution readers Antonio Caso, Sharon Barry and Shabon!