One of the more unique items we’ve come across in WoW is the Haunted Memento. This item, a fairly common drop from certain mobs during the scourge invasion event leading up to the release of the Wrath of the Lich King expansion, allows for your character to be followed around by a shadowy phantom.
The Haunted Memento can be traded with other players and even thrown to others (thereby haunting someone else). It is in this tradable nature of the item that we begin to see the WoWenomic value of holding on to these Mementos long term. Assuming that there are no future opportunities to attain one, they can only go up in value. Already they are regularly selling in the Auction House for 800 or more whereas they sold for less than 200 during the actual event. Should you decide to pick a few of these up for resale at some point in the future (perhaps, for example, well into the release of Cataclysm) they should fetch a hefty sum on the market. Of course, as we mentioned, buying and holding these also assumes Blizzard will not make them more readily available at another time so trade at your own risk.
If you’re going to get into the Haunted Memento market you will want to be aware that it is a unique item. If you are storing them long term, you’ll have to get creative in how you do so. One suggestion is to mail them between characters and, if necessary, even level one alts as there is no level requirement to having one.
At any rate, conduct a few scans for this item on your server’s AH and see if you can’t pick a couple up at a reasonable price and store them away for sale some point in the future. Currently, we try to purchase them at prices lower than 400 gold and resell them in the realm of 1,000. The best deal we’ve found was 100 gold but such deals are rare. You might also try your luck advertising for these items in the /trade channel but do so sparingly as the market is fairly small and a savvy trader will want to steer clear of any otherwise avoidable competition.