Leatherworking

Leatherworking is a crafting profession which uses hides and leather gained by Skinning to craft armor, armor kits and drums.

Leatherworking is typically desired by leather-wearing classes ( Druid, Rogue) and mail-wearing classes ( Hunter, Shaman), but other players can benefit greatly from the powerful armor kits they can craft, particularly the leg armor kits which provide non-casters with the greatest possible enchant for that slot. As such, they fetch a nice price on the Auction House and are a great moneymaker for any leatherworker.

Leatherworkers can also create starter PvP sets and decent capes. In addition, leatherworkers can create several larger bags for profession-related items.

Leatherworkers are capable of creating various drums which have multiple charges and can be used to provide a buff to players in their raid, including two (somewhat weaker) exclusive versions of other classes' raid buffs - Drums of Forgotten Kings and Drums of the Wild.

Leatherworkers can craft some Stylin' vanity hats, for which the patterns drop in BC dungeons. There's also the temporarily and silly enhancement Pattern: Comfortable Insoles.
Profession-specific Perk
Leatherworkers learn exclusive Fur Lining spells in Wrath and Draconic Embossment spells which they can use to enchant their bracers with buffs far more powerful than those available from Enchanting. In addition, leatherworkers can make BoP leg armor kits for a fraction of the cost.

Throughout the expansions, there have been recipes that create BoP armor. In some tiers, these items have proven to be best-in-slot.