Here is a list of the items found in Diddy's Kong Quest.
Bananas - collecting 100 grants an extra life. Banana bunches are worth ten bananas.
Animal Crate - contains an Animal Buddy.
KONG Letters - finding all four letters on a level grants an extra life.
Hot Air Balloons - used to float over dangerous ground safely.
Crates - can be used to defeat enemies.
Treasure Chests - when broken, usually contain a prize. Can also be used to defeat enemies.
Extra Life Balloons - grant an extra life.
DK Coins - hidden by Cranky in every level and must be obtained to finish the game.
Banana Coins - used as currency in the game for services from the Kong family.
Kremcoins - prizes upon completing bonus games and used to access Lost World.
Kannons and Kannonballs - putting Kannonballs inside of Kannons opens up bonus areas.
Target - found at the end of a level, gives an award if jumped on from far above.
Skull Cart - ridden like a mine cart in certain levels.
Golden Feathers - only found in the Gameboy Advance version of the game, they're used to upgrade Expresso II in the Expresso Racing minigame.
Scrapbook and Photographs - only found in the Gameboy Advance version of the game.