The Legend of Zelda: Ocarina of Time/Secrets

Giant enemies
If you repeatedly kill some types of enemy within a short period a giant version will appear. This applies most to the Skeletons running rampant during the night on Hyrule field.

Never lose tunics and shields
When a Like-Like is eating you swap to the Kokiri Tunic and Mirror Shield. Because neither can be purchased nothing in the environment is able to destroy them, and so the Like-Like can't eat them.

Free money
As young Link, travel to the gate in front of the city. Stand on either chain, and wait until night. The gate will be raised. Walk across the narrow end of the upturned gate to collect your free money.