Chimney

Left alone it sits there looking like the top of a fireplace. Wire it and each pulse steps it forward: first a thin trail of smoke, then a heavier version whose puffs drift and wobble the way bubble machine output does. One more pulse and it goes quiet again.

The heavier setting is the one worth wiring, since those particles rise well above the block they come from and sell a lived-in roofline from across the map. Put the emitter at the peak of the stack rather than the base, or the smoke pushes up through your own tiles. It does nothing mechanically, so treat it purely as set dressing on a build you already finished.