Donkey Kong Land 3

All levels complete:
Press Left(2), Up, Down, Right, Left(2), Down, Up, Right, Left(2), Up, Down, Right. Open a saved game and all levels will be marked completed, with the exception of bonuses.
Information in this section was contributed by Carlo The Great.

Unlimited lives:
Press Down(2), Up, Left, Right at the title screen. Note: This code has no effect in time attack mode.

Sheepy Shop mini-game:
Press Up(2), Down, Left, Right at the title screen. A sound will confirm correct code entry. Begin game play to start the Sheepy Shop card matching mini-game.

In-game reset:
Hold Start + Select and press A + B.

Leave previously completed levels:
Pause game play, then press Start + Select.

Time Trial mode:
Collect all items in the game (Clocks, DK Coins, etc.) and defeat K-Rool in the final battle. The "Time Trial" option will be unlocked the next time the game is played.
Information in this section was contributed by oxnard.

Unlimited bear coins:
Complete the "Lift Shaft Lottery" in the Cape Codswallop world. Enter it again, move left and collect the bear coin. Press Start + Select to exit the level, then replay the level to collect the coin again. Repeat this to collect as many coins as needed.

Bonus lives:
Play the "Total Recoil" level in the "Cape Codswallop" world. Collect the extra life in the bonus stage, intentionally lose the present life, and repeat.

Bonus level:
Go to the Cape Codswallop - Total Rekoil level. Jump left when starting the level to find a bonus stage.

Hint: Karbine Kaos: Unlimited coins:
In Great Ape Lakes, go to Karbine Kaos level. Use Kiddy to run and jump on the rat to get a Bear Coin. Press Start + Select and repeat to get unlimited coins to play Sheepy Shop mini-games.
Information in this section was contributed by KoopaKid16.

Hint: Sea Bed Shanty: Warp barrel:
There is a warp barrel in the Sea Bed Shanty level in Cape Codswallop. Move right then down and left to get Enguarde. After you get to the fourth Shark pit, swim up to the farthest pit sticking out. Directly up where the three bananas are sticking up, you will find a warp barrel that leads you to the end.
Information in this section was contributed by KoopaKid16.