The Legend of Zelda: Breath of the Wild’s official Japanese blog has detailed exactly how amiibo work in the game.
Link (Archer) gives the player meat, fish, bows, and arrows.
Link (Rider) gifts mushrooms, weapons, and horse tools.
Zelda will provide shields and plants.
Bokoblin offers meat and weapons.
And lastly, the Guardian will gift some “ancient materials”.
Scanning the Super Smash Bros. series Zelda amiibo will give players special chests full of items, while any other amiibo will offer meat and fruit.
The Legend of Zelda: Breath of the Wild and its line of amiibo launch on March 3rd, 2017.