Note: This bug is unpredictable, as it focuses mainly on lag. It is also unpredictable because of the type of item the mobs drops when it dies.
Anyways... Here's the bug:
When you kill something, right before it drops an item, unplug your internet connection. Now, as said, this is unpredictable. You might not reconnect when you plug it back in, or the mob might drop nothing. You also have to time it perfectly, because the game might boot you.
Anyways, plug it back in before you get booted.
I've come back with about six of the same items lying on the ground. Sometimes more, sometimes less. It all depends on how long you dare to go LD.