Get New Outfits:
Finish the game one time

Translate Hylian->English:
If you complete the game the text in the Hylian language will now be displayed in English.

Deluxe Picto Box:
After completing the game Link wil start his new adventure with the deluxe picto box (you can take color photographs instead of black and white).

Aryll's Skull Dress:
Aryll will have the purple "skull" dress on throughout the game. To get this simply complete the game.

Fairy Upgrades:
There are eight different possible fairy encounters in Wind Waker -- and each leaves you with a very helpful upgrade.
There are six standard fairy wells. Upgrades are typically given in this order, independently of which fairy you visit at what point in the quest:
1. Bigger Wallet: holds 1,000 rupees
2. More Bombs: 60
3. More Arrows: 60
4. More Bombs: 99
5. More Arrows: 99
6. Bigger Wallet: holds 5000 rupees

Northern Fairy Island
Requirement: Bombs

Outset Island Fairy Well
Requirement: Deku Leaf, Bombs

Western Fairy Island
Requirement: Skull Hammer

Eastern Fairy Island
Requirement: Bombs

Southern Fairy Island
Requirement: Bombs

Thorned Fairy Island
Requirement: Skull Hammer

Additionally, there are two special fairies:

Mother & Child Isle Fairy
Requirement: Balled of Gales
Simply warp to this island with the Ballad of Gales and you will receive the Fire and Ice Arrow upgrades (once you have the Hero Bow)

Big Octo Fairy
Requirement: Boomerang or Bombs
Look for the swarm of seagulls in the quadrant and shoot the Octo's eyes to free this fairy. She will double your magic meter.