Fish
These fish can be captured in bottles in the lands of Termina and Hyrule. They are needed to gain entrance to Lord Jabu-Jabu's belly in Orcarina of Time. It seems that despite that these Fish are easy to find, they are can be quite valueable if you're looking to get some easy money. However, only certain people will offer to trade with you.
Fish can also be captured in A Link to the Past when the water is drained out of a certain pond in the south of the Light World. If this fish is thrown back into the water it will say "thank you" and throw you some rupees.
In Twilight Princess a fish has to be caught at the beginning which a cat then steals and runs off into the shop, this then unlocks the slingshot in that shop.
Also later on a fish called the Reekfish needs to be caught using a Coral Lure in Zora’s Domain.
In Oracle of Seasons it is the sixth item in the Oracle of Seasons trading sequence. This is a blue small fish. Given by Ingo in exchange for helping complete his vase collection with the Goron Vase, which was always refuesed to him by Biggoron. This fish is passed on to an old man trying to get his cat down from a tree in Eyeglass Lake, in return for the Megaphone.
Types of Fish
Legend of Zelda Links Awakening
The Wind Fish
Legend of Zelda Ocarina of Time
Legend of Zelda Majora Mask
Legend of Zelda Wind Waker
Map Fish, Gyorg
Legend of Zelda Twilight Princess
Greengill, Hyrule bass, Hylian Loach, Hylian Pike, Ordon Catfish, Reekfish,