It's a variation of the Swordless Link trick. Please note, you need THE MASTER SWORD for this trick to work. First, you get the rod, put on your hover boots, and while Link's hovering, cast at the water. Then, you go outside, with the fishing pole. Then, you cast near an enemy, get frozen, and be unfrozen by an attack. Then, after you leave, you'll have the beta Deku Stick, only it'll replace the Biggoron Sword INSTEAD of the Master Sword. Save and reset the game. Remember to refrain from using the deku stick, because it'll freeze the game. Now, here's the part which suprised me. Go to Goron City and get into Medigoron's Blade Shop. pay him the standard 200 rupees to buy the Giant's Knife. Once you pay, go into the Equipment Subscreen. You now have the Biggoron Sword AGAIN!