I'm a big fan of SciFi's greatest strategic weapons, which generally involve heavy things falling from space to surface. From the Heavy Gear roleplaying game universe we had "ortillery" (orbital artillery), manned and unmanned platforms dropping tungsten rods from medium orbit.<br /><br />Another favorite is from Mobile Suit Gundam. Don't like someone? Drop a whole city on them. A />20km long O'Neil colony cylinder deorbited upon your terrestrial enemies is the ultimate big stick.<br /><br />Lastly, the asteroids thrown by the Bugs in the Starship Troopers movie (it's been so long since I've read the book, I don't remember if this was created for the movie or not). Sure it's just a rock falling from space, but what's really impressive is the work behind it: the asteroid seems to be flying at sublight speeds, so Queen Bug needs to become aware that, y'know, in a couple million years the monkey-things on that planet next to the yellow star are going to evolve and get uppity, so she should have some plasma-bugs fire at the local asteroid belt to kick some rocks onto an interstellar trajectory that will intersect Earth right around the time the two species go to war. And just for good measure, she sets it up to nail a major city that will be built by the as-yet nonexistant enemy. Woah. <br /><br />None of these are really going to hang over the fireplace though, so let's go with the gyroc, a low recoil rifle and pistol firing spin-stabilized rocket propelled bullets. So science-fictiony, they really built it.