Frostmaul Giants in Winterspring are worth farming just for the Greater Frost Protection Potion recipe they drop. These guys are pretty tought but the drop rate is good and on some servers the recipe has potential to sell for hundreds of gold.
Frostmaul Giants (level 55-60 elites) in Winterspring have about 2% drop rate for Recipe: Greater Frost Protection Potion. The median price for this recipe is 60 gold so they are well worth farming for. On some servers it sells for much higher prices so you'll better check your Auction House for going prices on this item. The giants are level 55-60 elites so it sure won't hurt to be a Hunter or a Warlock when trying to solo them.