I'm new here, hope this hasn't been posted yet. If it has, sorry for wasting your time.
Idea: Hank is buying a Krol Blade from Marcus for 450g. Hank puts in gold, see's Marcus's Krol Blade, and scrolls down and clicks accept. However, he has no Krol Blade, just a cruddy level ten weapon.
What you need:
-An Epic item.
-A cruddy gray/green weapon, with the same avatar as the epic.
-The scamee.
The Plan: First of all, make sure you got an Epic weapon, and shout something like "WTS [Epic] 450g!" Generally, something lower than it's normal price, so you're flooded by customers. Pick one, usually the one who is highest level. Find him/her, and here is the tough part. Wait for them to put in their gold, then put in your Epic, then immeditally switch your Epic for your cruddy weapon with the same avatar. If done correctly and fast enough, the victim should of clicked accept right as you switched. Accept, ignore, and run away with the loot.