Player Trading
click on another player and see a trading inventory view, maybe 9 slots each player
as players move items into their "you give" inventory, the other player can see it in their "you get" inventory
if both players click accept then the goods are traded
If you are interested in coding this let me know and i'll take this post down and let you make a [Mod] post.
If you would like to see this coded please leave a comment and I will have a crack when I get some time.