Out of the items here, this really is the one that requires a profession and level to use. Engineers with a level of 245 can wear the Green Lens, which can be a nice way to mywowgold Classic wow gold knock some contest as the thing itself is the BiS for several classes. Elemental Shamans and Balance Druids are only two of several examples.
This trinket which makes it infamous for starting fights and has a low drop rate, is sought after by courses, fracturing guilds, and destroying friendships. Guilds will frequently farm for this item as many of Druids and the Mages have it as you can to be sure. It is not the drop rate of the product that is low, it is that it drops from a rare spawn in Blackrock Spire named Jed Runewatcher. The trinket may not drop, so get prepared to farm BRS a couple of times before you see this item, even though Jed does pop up.
The Truefaith Vestments are spec and class-specific, intended only for Holy Priests, because it is main skills are restoring mana and providing a generous fan to healing spells. They're also among the easier things on this list to achieve, especially if you're a Tailor.
The quest for the Truefaith Vestments is about awaiting the pattern than really getting the item itself to fall. That means seeing Stratholme to kill the demon Balnazaar or Grand Crusader Dathrohan. You do not have to be a tailor to wear them, although you need a level of 300 to make them.