OKAGE: Shadow King

This is a side quest that you can start near the beginning of the game. After the events unfold and your adventure begins, speak to your grandma to obtain a pebble for the bakery shop owner. Head to the bakery shop owner in Tenel and trade the pebble for some bread crust. Go to Tenel Forest, and head to the the first bridge. Go under the bridge and trade the crust to the painter for a worn paintbrush then head to Madril and when you arrive, head for the Gear Freak's house on the first floor to the North. Trade the paintbrush for a big gear. Next, when you get to Rashelo, head to the lighthouse and talk to the sailor to trade the big gear for a penlight. After that, head to Highland then talk to the man in the lone house towards the East and trade the penlight for a broken gun. Take the broken gun back to your house and talk to your father. He will trade you the Unicorn Horn for the broken gun.