Lately I've been playing the 3DS remake of Legend of Zelda: Ocarina of Time. And as its status as one of the most popular games in history might suggest, it's pretty damn good! In fact, I've rather gotten into the LoZ series as a result, and I'm probably going to pick up another game when I defeat Ganondorf - what with Majora's Mask being released just yesterday, I guess I'd better get on that.
As for this particular chain of events: it seems that convoluted trading quests are a staple of the franchise. OoT's nets you Biggoron's Sword, a claymore of epic strength and epic length, outstripping even the Master Sword in power. Truly it's a fine weapon... but my god, the hoops you have to jump through to get it! If you've not experienced this quest for yourself, allow me to break it down for you:

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The quest starts when you talk to Anju the cucco keeper in Kakariko Village. She gives you the egg for her new "Pocket Cucco", which will hatch after a day (presumably filling Link's pocket with egg yolk). The newly hatched cucco must then be taken to the sleeping Talon in the village, and it will crow and wake him. Take the cucco back to Anju, and she'll trade it with a special blue cucco called Cojiro. Take Cojiro to the Lost Woods in Kokiri Forest and navigate the maze until you come across Grog. Show Cojiro to Grog and he'll declare you "a nice guy" and ask you to take an Odd Mushroom to the potion hag back in Kakariko. This particular leg of the quest is on a three-minute time limit - and don't even think about using the Ocarina of Time as a shortcut to warp across Hyrule, it'll expire as soon as you appear. Riding Epona across the field is fine, though - in fact, Epona is all but vital to this quest.
Bring the Mushroom to the hag in the back of the potion shop (and even figuring out that's where she was gave me quite a bit of trouble) and she'll mix it into an Odd Potion (which actually appears to be a poultice) to take back to Grog. Go back to the Lost Woods to where Grog last was. Unfortunately, he's gone missing - local creepy child Fado informs us that he's got lost in the Lost Woods and probably died and become a Stalfos. Seeing the Odd Potion/Poultice in your possession was made from Kokiri mushroom, she confiscates it and gives you a Poacher's Saw that Grog left behind. Take the Poacher's Saw to Mutoh the carpenter in Gerudo Valley, and he'll trade this "old, but well-cared for" tool for... a broken sword. Granted, the ultimate goal of this literal runaround is to get that stub of sword fixed, but I still can't help but feel I'm getting the short end of this exchange.
With the sword (or at least the hilt) in your hands, go to the summit of Death Mountain to bring it to the aptly-named Biggoron. This reputed Goron blacksmith can repair the broken sword, but the recent eruptions of Death Mountain have filled his eyes with volcanic ash, and he needs eyedrops before he can work. He gives you a Prescription to take to King Zora under Lake Hylia. Unfortunately, Ganondorf's depredations and sorcery have frozen the Zora's Domain solid, and King Zora himself is frozen in red ice. In order to get anything out of the regal piscine fatty, you need to go past him to Lord Jabu-Jabu's pool (luckily King Zora's still moweeped out of the way from Child Link's time) and find your way into the Ice Cavern for a bottle of blue fire (and the Iron Boots while you're at it).
Pour the blue fire on King Zora to thaw him out and give the Prescription to him. He doesn't have Biggoron's eyedrops himself, but he does have the requisite ingredients: an Eyeball Frog. Take this amphibian (again, within three minutes) to the Lake Scientist in his house by the drained Lake Hylia. Once the old coot's been convinced that the Eyeball Frog is not for his dinner, he'll mix it into the World's Finest Eyedrops, which you must then take back to Biggoron. This section too has a time limit, of four minutes this time - but in that time you'll need to travel to Death Mountain climb the path up, dodge the volcanic ejecta raining upon you on the approach, clear the Skulltulas off the climb-way up to the summit and finally ascend the mountain. Once Biggoron has finally cleaned the ash out of his eyes, he'll happily fix up your broken sword, but it'll take three days to repair. Unlike the rest of the quest though, you can skip this bit with the Sun's Song to fast-forward time. Talk to Biggoron again, and congratulations! You got Biggoron's Sword!

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So yeah, this mighty weapon takes some getting, ad even knowing what I was doing, it was quite close at some points. But yes, it is worth it - the bloody thing is absolutely lethal. Taste my steel, Ganon!