Buck Bumble

Full health, ammunition, all weapons
At the title screen, press Left, Right, Up, Down. Then, hold Z and press Right(2), Left(2). If you entered the code correctly, you will hear a sound. Then while playing the game, press A + B + R for full health, full ammunition, and all weapons.

Level select
At the title screen, hold Z and press Right, Down(2), Right. Release Z, then press Right, Up, Down, Left(2), Up, Right(2). If you entered the code correctly, you will hear a sound.

Invincibility
At the title screen, hold Z and press R(2), L(2), Up, Down, Left, Right. If you entered the code correctly, you will hear a sound.

Play as Dark Stinger
Before the opening screen appears, hold Z + Analog-stick Up and press C-Up, C-Right, C-Down, C-Left(5), B, A, B. If you entered the code correctly, you will hear a sound.

Faster text
Press Z to scroll the text dialogue quicker.

Skip text
Press A to bypass the current text dialogue.

Game Shark Codes

Infinite Lives -- 810E9652 0005
Infinite Health -- 810E92D8 42B0

Infinite Ammo
810E92E6 03E8
810E92EA 03E8
810E92EE 03E8
810E92F2 03E8
810E92F6 03E8
810E92FA 03E8
810E92FE 03E8
810E9302 03E8
810E9306 03E8
810E930A 03E8
810E930E 03E8

Have All Keys -- 810E92E0 0101 800E92E2 0001