ItemType

These are the possible itemType and itemSubType returns of GetItemInfo.

Item Types and Item Sub Types
Every item in the game has a type and subtype of some kind. No valid item will return nil for either of these values. Be aware that the strings are localized on the clients.

Possible itemType returns
"Armor", "Consumable", "Container", "Gem", "Key", "Miscellaneous", "Money", "Reagent", "Recipe", "Projectile", "Quest", "Quiver", "Trade Goods", "Weapon" for English client. Generally they are the same strings you see in the auction search tab.

Sorted Types and Subtypes
Armor
 * "Miscellaneous" - includes Spellstones and Firestones
 * "Cloth"
 * "Leather"
 * "Mail"
 * "Plate"
 * "Shields"
 * "Librams"
 * "Idols"
 * "Totems"
 * "Sigils"

Consumable
 * "Food & Drink"
 * "Potion"
 * "Elixir"
 * "Flask"
 * "Bandage"
 * "Item Enhancement"
 * "Scroll"
 * "Other"
 * "Consumable" - Seems some items still show up as this in 2.4.2 (Fel Blossom, Weighted Jack-o'-Lantern)

Container
 * "Bag"
 * "Enchanting Bag"
 * "Engineering Bag"
 * "Gem Bag"
 * "Herb Bag"
 * "Mining Bag"
 * "Soul Bag"
 * "Leatherworking Bag"

Gem
 * "Blue"
 * "Green"
 * "Orange"
 * "Meta"
 * "Prismatic"
 * "Purple"
 * "Red"
 * "Simple"
 * "Yellow"

Key
 * "Key"

Miscellaneous
 * "Junk"
 * "Reagent"
 * "Pet"
 * "Holiday"
 * "Mount"
 * "Other"

Money - Badges and other "linkable items" used as money

Reagent
 * "Reagent" - I think this is defunct

Recipe
 * "Alchemy"
 * "Blacksmithing"
 * "Book"
 * "Cooking"
 * "Enchanting"
 * "Engineering"
 * "First Aid"
 * "Leatherworking"
 * "Tailoring"

Projectile
 * "Arrow"
 * "Bullet"

Quest
 * "Quest"

Quiver
 * "Ammo Pouch"
 * "Quiver"

Trade Goods Weapon
 * "Cloth"
 * "Devices"
 * "Elemental"
 * "Enchanting"
 * "Explosives"
 * "Herb"
 * "Item Enchantment" (4.0.1: Consolidation of previous subtypes "Armor Enchantment" and "Weapon Enchantment")
 * "Jewelcrafting"
 * "Leather"
 * "Materials"
 * "Meat"
 * "Metal & Stone"
 * "Other"
 * "Parts"
 * "Trade Goods" - Some items still show up as this in 2.4.2 (Mountain Silversage)
 * "Bows"
 * "Crossbows"
 * "Daggers"
 * "Guns"
 * "Fishing Poles" (used to be "Fishing Pole" before 2.3)
 * "Fist Weapons"
 * "Miscellaneous"
 * "One-Handed Axes"
 * "One-Handed Maces"
 * "One-Handed Swords"
 * "Polearms"
 * "Staves"
 * "Thrown"
 * "Two-Handed Axes"
 * "Two-Handed Maces"
 * "Two-Handed Swords"
 * "Wands"

(for the purpose of [equipped: ] these can be used)
 * "One-Hand"
 * "Two-Hand"