Restore watermelon meter
When low on health, get next to a "Tag Barrel", jump into the barrel and exit to replenish your watermelon meter.

Swim faster
When swimming above water, hold B to swim faster.

201st Banana
Collect all 200 known Bananas so that Donkey Kond gets his board back. After collecting all 20 Bana Fairies, a message requesting you to visit the Head Fairy will appear. Visit her with Tiny and she will show you the way to the 201st Banana.

Rainbow Coins
Locate the dirt mounds marked with "DK" scattered throughout the game. Stand on top of a mound, then hold B to attack and send a shockwave to destroy the mound. A large Rainbow Coin will appear that results in five Banana Bunch Coins for each Kong.