I think this is easy to make: a trash. My idea is to have a command "/trash" or "/trash hand" that deletes what you have in your hand. Another one could be "/trash inv", which deletes all your inventory. I found this earlier: http://forums.bukkit.org/threads/misc-clrinventory-clear-your-inventory-v1.957/ I hope someone can make this
there are already inventory cleaners. http://forums.bukkit.org/threads/misc-clrinventory-clear-your-inventory-v1.957/
Portable garbage can: 1. Throw all your garbage to one block 2. Light that block with flint and steel Although plugins like /clean are still best, since they clean whole inventory with few keyboard presses. Very handy on servers, where people can spawn items.