Once we have mastered space travel, the most dangerous weapon that will be available to almost anyone will be firing an asteroid at a planet.

For another take on Kinetic impactors try The moon is a Harsh Mistress or as they call them. Tossing rocks down the gravity well.

There was one in the G.I Joe movie.

Mollari disgust level: Rising.

I'm gonna leave this here. Excellent video by Veritasium, looking at the practicality and plausibility of "rods from god"

https://en.wikipedia.org/wiki/Kinetic_bombardment

2003 United States Air Force proposal

A system described in the 2003 United States Air Force report called Hypervelocity Rod Bundles[10] was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods that are satellite-controlled and have global strike capability, with impact speeds of Mach 10.[11][12][13]

The bomb would naturally contain large kinetic energy because it moves at orbital velocities, around 8 kilometres per second (26,000 ft/s; 8,000 m/s; Mach 24) in orbit and 3 kilometres per second (9,800 ft/s; 3,000 m/s; Mach 8.8) at impact. As the rod reenters Earth's atmosphere it would lose most of its velocity, but the remaining energy would cause considerable damage. Some systems are quoted as having the yield of a small tactical nuclear bomb.[13] These designs are envisioned as a bunker buster.[12][14] As the name suggests, the 'bunker buster' is powerful enough to destroy a nuclear bunker. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the launch warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. Hit-To-Kill Missiles or megawatt-class chemical laser). The time between deorbit and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a worldwide range. There would be no need to deploy missiles, aircraft, or other vehicles.

In the case of the system mentioned in the 2003 Air Force report above, a 6.1 by 0.3 metres (20 ft × 1 ft) tungsten cylinder impacting at Mach 10 (11,200 ft/s; 3,400 m/s) has kinetic energy equivalent to approximately 11.5 tons of TNT (48 GJ).[15] The mass of such a cylinder is itself greater than 9 short tons (8.2 t), so the practical applications of such a system are limited to those situations where its other characteristics provide a clear and decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is far more practical and cost-effective.[16][17][18]

The highly elongated shape and high mass of the projectiles are intended to enhance sectional density (and therefore minimize kinetic energy loss due to air friction) and maximize penetration of hard or buried targets. The larger device is expected to be quite effective at penetrating deeply buried bunkers and other command and control targets.[19]

The weapon would be very hard to defend against. It has a very high closing velocity and a small radar cross-section. The launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a much smaller magnitude compared to a ballistic missile launch. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.[20]

The phrase "rods from God" is also used to describe the same concept.[21] An Air Force report called them "hypervelocity rod bundles".[2]