See, this is why we all need to carry the ceramic tips of spark plugs around - you throw them at the window, the tip shatters. The way it shatters causes the entire window to fracture. Since it is safety glass on modern cars, it doesn't fall in and hurt anyone. It just turns into a spiderweb, and freaks out the motorist. And there is no recoil or debris to avoid. And they are small enough that you could carry many of them in your pocket without noticing...