Big Poe

In Ocarina of Time, ten of these ghostly creatures haunt Hyrule Field. The only way to defeat them is to be on Epona, and shoot them with arrows. After being defeated, you can catch them in a bottle and sell them to the Poe salesman. If you sell all ten of them to him, you will be given an empty bottle.

In Majora's Mask, the Big Poe appears behind you and goes straight for you. Move out of the way and shoot it with an arrow to kill it. Repeat and it shall fall.