The Legend of Zelda: Twilight Princess/Equipment

Equipment Upgrades are usually found by participating in some minigame, completing a collection, or doing a special event.

Armor
There are two armor upgrades that you get. One is necessary in order to continue the storyline, and the other is helpful in the Cave of Ordeals.
 * You get the Zora's Armor after following the spirit of the Zora Queen.
 * The Magic Armor is available for purchase in the shop at the corner of the Castle Town Square. Originally it costs 100,000 rupees, but you can help Malo Mart take over that shop and they will sell it for only 598 rupees. Give 1,000 rupees to Malo Mart to help them fix the bridge, then agree to take a barrel of hot springwater to a Goron by the bridge.  You can obtain this hot springwater from the creature outside of the Malo Mart in Kakariko Village. The Goron on the bridge will give you a piece of heart and the money needed for the second stage drops from 2,000 rupees to 200 rupees. Give them the 200, and head to Castle Town to pick up your new shiny armor.

Bomb Bags
Bomb Bags allow you to carry bombs. Each bag can carry one type of bomb. A Bomb Bag can carry up to 30 Bombs, 15 Water Bombs, or 10 Bomblings. The upgraded Bomb Bag can carry up to 60 Bombs, 30 Water Bombs, or 20 Bomblings.
 * You can purchase a Bomb Bag when you purchase bombs for the first time at Barnes Bomb Shop.
 * You get a Bomb Bag after helping Iza unblock the river in Lanayru Province. A quick battle with shadow beings convinces her that you're able to handle the task.
 * You can find a Bomb Bag by blowing up the giant rock underwater in the throne room of Zora's Domain.
 * You can earn the upgrade for all of your Bomb Bags by scoring 25 points or greater on Iza's Rapid Ride.

Bottles
Bottles are versatile items that store things like lantern oil, potions, and fishing bait. There are four bottles in Hyrule.
 * You get a bottle after you return the cat to Sera's Sundries. The bottle is half-filled with milk.
 * You can buy a bottle from Coro for 100 rupees. The bottle comes filled with lantern oil.
 * You can bobber fish for a bottle in Hena's Fishing Hole. Head to the bridge on the side, and fish over the other side of the bridge. You'll eventually reel in a bottle.
 * You'll receive a bottle after you give 20 Poe Souls to Jovani.

Quivers
You receive Quiver upgrades when you successfully complete the STAR minigame. You will need the Clawshot for the first go-round to get the Big Quiver (60 arrows) and the Double Clawshots a second time for the Giant Quiver (100 arrows).

Hawkeye
The Hawkeye acts as a "sniper scope" for your bow, allowing you to zoom in. During the day, climb to the top of the cliff in Kakariko Village and talk to Talo to play a mini-game. After the game, win or lose, you can purchase the Hawkeye from Malo Mart.

Shields
Shields are handy items that protect you from harm. There are three shields in the game, but you can only have two of them at a time.
 * The Ordon Shield is acquired through the storyline.
 * The Wooden Shield is a replacement if the Ordon Shield burns up. You can buy it in the Kakariko Village Malo Mart.
 * The Hylian Shield is a handy shield. The cheapest spot to get it is the Kakariko Village Malo Mart.

Swords
You will receive three different swords, and one sword upgrade, during the course of your adventure.
 * The Wooden Sword is in your house. Take it out of a chest.
 * The Ordon Sword is acquired through the storyline.
 * The Master Sword is pulled from a pedestal in the Sacred Grove.
 * The Light Sword is an upgrade to the Master Sword found in the Twilight Realm.

Wallets
Wallets hold your money. The bigger your wallet, the more you can spend (and the longer you can be protected by the Magic Armor). You get wallet upgrades by giving Golden Bugs to Agitha. Giving her one insect nets you the Big Wallet (600 rupees), and giving her all 24 nets you the Giant Wallet (1,000 rupees).

Ammunition
Your ranged weaponry requires ammunition to be of use. If you run out of arrows for your Bow or seeds for your Slingshot, you'll have to find some more before being able to shoot with either one. Both types of ammo can be found in small chests, grass, rocks, pots, etc. In addition, seeds can be found by killing the Deku Baba enemy.

Keys
When in dungeons, you'll need to find various keys to progress. Small keys can be found in chests or by defeating enemies (usually mini-bosses), and are used to unlock doors to other parts of the dungeon. Along with varying amounts of small keys, there is also one boss key, which is always found in a boss chest. The boss key is usually found towards the end of the dungeon, and accessing the boss chest usually involves a puzzle of its own.