Blacksmithing is a great profession if you are into actually building the armor and weapons. These are the 305-350 WOW recipes that you can find and train in as a master blacksmith.
Jewelcrafting focuses on taking raw gems out of ore and cutting them into items that can be socketed into armor and weapons that give major statistical increases. Different classes favor different gem types. Each gem has a color which correlates with what the gem itself does.
In World of Warcraft, enchanting can be a great profession if you are into altering the effects of armor and weapons. These are the recipes that you can find and train in as a master enchanter.
Engineering is a unique tradeskill that doesn’t have any particular focus. Many engineering items provide special skills that are generally only available to a single class.
Cooking is a secondary tradeskill that any serious WoW player should have capped out on at least one character in their account. The buffs that good food provides are indispensable, often equivalent to a minor gear upgrade.