PlayerObserver-Helper by Moertel
This Plugin enables you to observer the inventory of other players. If you enter the plugins command and have the necessary permission to use it, an inventory will show with every player that is currently online. You can select the player of your choice and choose between his enderchest inventory of regular inventory.
The only command this plugin uses is /pohelper (<Playername>). The playername is not necessary as you will be able to select the player of your choice anyways.
There is only one permission needed: pohelper.use
If you have that permission you are able to use the /pohelper command and therefore manipulate other players inventories.