It has been suggested that militaristic civilizations will not develop spaceflight; the reason being that any aggressive civilization will sooner destroy itself. I think this is rather true. To be more specific, any civilization with the capacity for interstellar travel, if even the lowest grade of travel that takes centuries, will have acquired simple means of destroying themselves. Interstellar travel implies the capacity to accelerate and propel large masses to high velocities, possibly near-relativistic speeds. In other words, any space-faring vessel is necessarily a weapon.
In that vein, I wonder if a simple means to create a weapon of mass destruction is to simply launch a tungsten probe into space, let it acquire velocity through gravity-assists, and redirect it at a planetary target. If the probe is sufficiently hardened to survive reentry, then this is essentially an artificial meteor impact.
It would be a fitting weapon for any bond villain, and probably cheaper and easier to build and acquire than a nuclear weapon.