The Masks

Keaton Mask- Sell it to the guard in front of Death Mountain.
Skull Mask- Sell it to the skull kid in the lost woods.
Spooky Mask-Give it to the kid in the kakariko graveyard.
Bunny Hood- When you are an adult, go to the entrance way of gerudo valley. Race the marathon runner. Now come back to the area near the valley in Hyrule Field to find him.Follow the marathon runner until he stops for a break. Put on the mask and talk to him.
Mask of Truth-Get it from shop after you sold everything. You can look at the One-eyed statues with this. They will tell you some gossip.
Goron Mask-It is free to borrow after you get all the masks. It's only use is to make yourself feel at home in Goron City.
Zora Mask- It is free to borrow after you get all the masks. It's only use it to make yourself feel at home in Zora's Domain.