Ocarina Of Time 3D Biggoron Sword
You must have Epona and unfrozen King Zora in the future in order to complete this quest. It is highly recommended that you plant a Magic Bean in front of Dodongo's Cavern. The following Ocarina of Time 3D Biggoron Sword Guide covers every part of the trading sequence.
Ocarina of Time 3D Biggoron Sword Guide
Go to Kakariko Village and find the cucco lady. She will give you an egg. Either play the Sun's Song a couple times OR run around Hyrule Field until the egg hatches. Go find Talon in the building directly in front of the entrance to the village. Use the cucco to wake him up. Go back and show the cucco lady the cucco.
Upon showing the Pocket Cucco to the lady, she will tell you about her brother's cucco. She will give you the blue cucco, Cojiro.
Enter the Lost Woods and head down the path to the left. There is a man sleeping near a stump. Stand in front of him and use Cojiro to wake him up. He will give you the Odd Mushroom and tell you to take it to the lady at the potion shop Kakariko Village. There is a 3 minute timer, so make sure to use Epona in order to make it to the village quickly. Use the hookshot to get on top of the potion shop. Now just enter and show the mushroom to the lady. She will make Odd Poultice out of it and tell you to take it back to the man in the Lost Woods.
Take the Odd Poultice back to the spot where the man was in the Lost Woods. The man will now be replaced with a Kokiri Girl. Show the Odd Poultice to the girl and she will ask you to return it. Afterwards, she will give you the Poacher's Saw.
Take the Poacher's Saw to Gerudo Valley. There is a Carpenter's Tent with a man standing out front. Show the Poacher's Saw to him and he will trade you a Broken Goron Sword in return.
Broken Goron Sword
Take the Broken Goron Sword to the summit of Death Mountain and find Biggoron. Show him the Broken Goron Sword and he will tell you he is unable to fix it because the volcano eruption has irritated his eyes. He will give you a Prescription for some eye drops.
Take the Prescription that the Biggoron gave you to King Zora in Zora's Domain. King Zora will give you an Eyeball Frog and tell you to take it to the Lakeside Observatory before it expires
There is a 3 minute timer on the frog. Quickly travel through the path to Zora's Domain using the river routes. Take Epona across Hyrule Field. You should be able to make it to the observatory in time. Talk to the guy and then show him the Eyeball Frog. He will give you the World's Finest Eyedrops.
World's Finest Eyedrops
The eyedrops have a 4 minute timer. Travel quickly back to Hyrule Field and get back on Epona. Go to Kakariko Village. Travel to Death Mountain and quickly make your way to Biggoron. Show him the eyedrops before the timer run outs and he will give you a Claim Check.
Claim Check and Biggoron Sword
After receiving the Claim Check, either run around for a few game days or play the Sun's Song several times. Once a few game days have passed, the Biggoron will trade the Claim Check for the Biggoron's Sword. Since the sword is two handed, Link will not hold a shield when using it.