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 these Fish are easy to find, they are said to be quite valueable if your 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 certian 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.