Here’s a good one from the Allied side of the fence. When we dropped a bomb on the Axis forces, we wanted to make sure it’d wreak as much havoc as possible. British engineer Barnes Wallace noticed that explosions were diffusing a great deal of their force into the air, wasting much of the explosive payload.
His solution was the “earthquake bomb,” a heavy explosive device with a super-hard pointed tip that would sink deep into the Earth before detonating, producing what basically amounted to a controlled earthquake. It worked as advertised and we used it to destroy many high-value German targets.