When i was trying to figure out a way to do the weapon and armor bug on my server (WoWgasm) i figured out a way to get more than one unique item.
Step 1: Place the items you want to have 2 of in your second bag.
Step 2: Place any item in the last slot of that bag. I used Blade of Wizadery since i had alot of them duped.
Step 3: WITH THE BANK WINDOW OPEN, right click the item in the last slot of the bag. This will put the bag into the bank.
Step 4: Now just go to the Mall area and buy the unique items again. Then go to the bank and put your bag back into its bag slot.
Note: I posted this because maybe someone can figure out a way to use for something more game-breaking. Also, If you right click on the first slot in that bag, it puts your helmet (that you have equipped) into the bank and greys out the item you right clicked, this is what i was messing around with when i found this out.
Also, if you relog while your bag full of items is in the bank, then log back in and equip the bag it will be empty. Then if you relog again the bag will have the items again, or it will put the items back into your bags where they were before you drug them into that bag.
credits to condump from Dsoft