>The Shiny Leaf (Japanese: かがやくはっぱ Shining Leaf) is an item found in Pokémon HeartGold and SoulSilver. It is a rare item that can be found by the player's walking Pokémon. When it is found by a Pokémon, it will have no apparent presence other than on that Pokémon's status screen. When a Shiny Leaf is shown to the player's friend (Lyra or Ethan) in New Bark Town, he or she will explain about them and request for the player to bring four more. When the player shows a single Pokémon with five Shiny Leaves attached to it, a star will be awarded for the Trainer Card and a certificate that can be viewed when the player speaks to their childhood friend. He or she will then craft the Shiny Leaves into a Leaf Crown, which can be seen on that Pokémon's status screen in the same spot the Shiny Leaves were. -Bulbapedia
>Despite the player's friend implying the opposite, the Pokémon's friendship has no effect on its ability to find Shiny Leaves.
No real use just you can make a cool item with it :D