Deku Leaf
The Deku Leaf is an item first introduced in The Wind Waker. It is obtained in the Forest Haven from the Great Deku Tree.
The Deku Leaf is incredibly useful as an item in two ways. Its first function is that of a makeshift fan. When used on the ground, link fans it very hard, causing a strong puff of wind to blow forward. This air puff can be used to blow apart piles of leaves, stun enemies, and turn pinwheels. However, it cannot go through walls or other objects, and once it hits its target, it stops moving and dissipates instantly. The air puff's usefulness is also detained in the fact that if Link has no magic power, the leaf wilts and cannot be used. The air puff itself, however, does not use any magic power.
The Deku Leaf's more important function is that of a glider. After jumping off of a ledge, using the items results in Link holding the leaf above his head and can glide for long distances, similar to Deku Link's flower propellers. Combined with a Boko Baba bud launch, the young hero can move vast distances with this item. However, it drains magic power rather quickly, and if Link is outside, he will need the wind to go in his gliding direction to get anywhere. This means that turning in midair while outside is mostly ineffective and eats up most of the magic power. If Link runs out of magic, the leaf wilts once again and is rendered useless until he gets his meter refilled.
Trivia
After using the Deku Leaf in middair, if the player continuously taps the button it is equipped to throughout its flight, it will actually reduce the amount of magic that it takes.