Nothing

Nothing has its own NothingItem class with exactly one overridden behaviour: right-clicking it (use()) makes it vanish, consuming one from the stack, except in creative mode, and the client/server report a "successful" interaction, but nothing actually happens. No sound, no particles, no entity spawn.

It shows up frequently in chests scattered across the origin world, the name and the concept are the joke: "Nothing," an item you find everywhere that does nothing at all.