I have a few:
- Chosen ones, fate, destiny, &c. When you get down to it, a story with these themes is one where a single person or handful of people is ontologically, cosmically better and more important than everyone else. It's eerily similar to that right-wing meme about how "most people are just NPCs" (though I disliked the trope before that meme ever took off).
- Way too much importance being given to bloodlines by the narrative (note, this is different from them being given importance by characters or societies in the story).
- All of the good characters are handsome and beautiful, while all of the evil characters are ugly and disfigured (with the possible exception of a femme fatale or two).
- Races that are inherently, unchangeably evil down to the last individual regardless of upbringing, society, or material circumstances.
There are stories that use it. The term "relativistic kill vehicle" gets used sometimes. Spin a rock up to a good fraction of c then delete a whole planet. Really depends on what the writer wants to do, though. Three Body Problem is the most recent famous example of "ftl big gun." Thing. Star wars has done it a bunch of times. One of the old comics had a star destroyer that fired planet cracker torpedoes through hyperspace. The ancient Lensman series has had every kind of variation of "strap ftl drive to object" you could imagine.wh40k orks hollow out asteroids, fit them with warp drives, then fire them at the next star system they want to invade. They crash the entire asteroid, or moon, in to the target planet as their invasion ship.
nods in galaxy gun
I ADORE Tom Veitch, but yeah that sums most of his work up in one sentence.