Patch 4.3 for World of Warcraft will finally allow players to transmogrify their armor, that is, to combine the stats of one piece of gear with the appearance of another. Warlock T5 anyone?
An update to the official World of Warcraft website features a preview of Transmogrification in 4.3 along with image examples of the system in work.
The short of it is this, bring your coin and gear to your local Transmogrifier, place the items into the device, and voila! There are a few restrictions though, you can only transmogrify items that have statistics on them, you can't combine different weapon or armor types, and you must be able to actually wear the item(s) you're combining.
Get the full details over at the official World of Warcraft website.