Bug Catching Net
In Kakariko Village, there's a house with a bed-ridden kid inside. He will give Link the Bug Catching Net if Link has at least one Bottle in his inventory.
The bug net allows Link to catch bees and fairies to store them in bottles. It can also be used to deflect the energy balls in the Agahnim boss fights. In speedruns, this is normally used for added safety with the ability to catch fairies.
Doing an Itemdash and bonking a fairy source can allow Link to instantly collect the fairy. This is commonly done on the Pegasus Rocks to the left of the Fortune Teller's Hut or on the left tree in front of the Pyramid.