HT Games
Weapons
Many one-handed weapons can be wielded in either hand, although some weapons are specifically designated as either main-hand or off-hand weapons, and their tooltips will state as such. Weapons held in the off hand will usually do 50 percent less damage, although most classes that can equip weapons in the off-hand slot have a talent that reduces this penalty by 25 percent or removes it completely. Warriors who specialize in the fury talent tree and assign a point to the "Titan's Grip" talent can equip two-handed swords, maces and axes as if they were one-handed weapons, allowing this character type to equip one two-handed weapon in the main-hand slot and one in the off-hand slot. Weapons equipped in the off-hand slot are displayed either at your character's waist or on his back, depending on the weapon's model, until you unsheathe your weapons by pressing the "Z" key, at which point they will be held in your character's left hand.
Shields
Classes with the shield proficiency can equip shields as an off-hand item. Characters with an equipped shield can use it to block some attacks, although only those who specialize in the tank role can block attacks often enough to make a difference. Shields serve only as protection and to increase certain stats. Characters may not damage enemies with their shield, although the name of certain abilities such as Shield Slam may lead you to think so. Any shield is displayed on your character's back until you unsheathe weapons by pressing the "Z" key.
Off-Hand Frills
The third type of item that can be equipped in the off-hand slot is the off-hand frill, identified on its tooltip as "Held in Off-Hand." Items of this type, designed for characters who specialize in the role of magic damage dealer, serve only to provide additional stats to the character. Off-hand frills can have a lot of different models, from flowers to crystals, books, lanterns and chalices; they are not displayed anywhere on your character unless you manually unsheathe your weapons by pressing the "Z" key.
Considerations
The three types of items that can be equipped in the off-hand slot are designed for different types of characters. Melee damage dealers such as rogues, enhancement shamans, fury warriors and frost death knights should equip a weapon in their off hand to deal more damage, while tank characters such as protection warriors and protection paladins should equip a shield in their off hand to mitigate some of the damage dealt by enemies. Holy paladins and restoration and elemental shamans can equip either a shield or an off-hand frill, and should choose whichever item has higher stats. Healers and magic damage dealers such as druids, priests, warlocks and mages can equip only off-hand frills and should always equip one when using a one-handed weapon to take advantage of the additional stats.