Zelda's Letter — Sneak past the castle guards (use the crates and the moat) and meet Zelda in the courtyard. Her letter opens the Death Mountain gate and the Happy Mask Shop.
Weird Egg — Malon gives it to you outside the castle while waiting for her father. It hatches into a Cucco after a day; use it to wake Talon by the gate.
Ruto's Letter (in a bottle) — Dive for the bottle near the Lake Hylia lab (the Silver Scale helps). Show it to King Zora and he shuffles aside to let you reach Zora's Fountain.
Claim Check — Final step of the trading sequence: deliver the Eye Drops to Biggoron and he gives you the Claim Check. See the Trading tab.
World's Finest Eye Drops — Trading sequence item from the lake scientist.
Eyeball Frog — Trading sequence item from King Zora.
Prescription — Trading sequence item from Biggoron.
Broken Goron's Sword — Trading sequence item from the master carpenter.
Poacher's Saw — Trading sequence item from the Kokiri girl in the Lost Woods.
Odd Potion — Trading sequence item from Granny's Potion Shop.
Odd Mushroom — Trading sequence item from Grog in the Lost Woods. Timed.
Cojiro — Trading sequence item from Anju.
Pocket Egg / Pocket Cucco — First trading item from Anju, the Cucco lady, as an adult.