Top 10 SciFi/Fantasy Tropes (and maybe a few off the cuff suggestions for changing them up)
1. Superpower/Chosen One - you know this one. Superman. X-Men. Avengers. Comic books. Movies. Selling lots of tickets to summer blockbuster movies. The Chosen One trope - The Hobbit. The Lord of the Rings. Guardian of the Galaxy. Any story that taps one character as The Savior of whatever the cause du cinema maybe. In these tropes, it should be noted, no one's ever just trying to save a puppy. It's the entire frickin' Universe. Always. Who knew we faced so many great, existential threats? CHANGING IT UP: The Chosen One trope is easy to alter, just go with 'it could have been anyone, but right here, today, it was me' or choose a group and forge a team - though this last one is a tiny bit trope-y, too, so it can't simply be a rehash of The Three Musketeers. You do need to have something to say about the macrocosm of society in your microcosm.
2. Parallel Universe(s) - Every permutation of possibility is fer REALS because parallel universes! All you need is one transporter malfunction to prove that you can function in universe not your own! Okay. Granted. This is now an actual hypothesis encompassed by string theory, though I doubt every much that most physicists buy into a sinister Mr. Spock. (Mirror, Mirror) CHANGING IT UP: This trope hasn't been entirely mined out yet, I don't think. There's plenty of room for interesting, clever parallel universe story telling. That said, before one ventures into a parallel universe, one should endeavor to answer a single question: WHY? What is it about that universe that shows up the characters or the central plot question better than this universe could? 'Cuz it'd be cool' is probably sufficient motivation for a Dungeons and Dragons game. In the basement.
3. Interstellar, Faster than Light Travel - Pretty much every scifi ever. Star Trek had warp drive. Star Wars had hyperspace. Farscape used wormholes. Dune folded space. Science fiction readers accept the trope of Faster than Light travel because few authors and few readers have the mathematical and scientific understanding to grasp a technical explanation of how faster than light travel might be possible. So we suspend disbelief and accept the shorthand because we'd just as soon get on with blowing shit up. DON'T CHANGE THIS ONE UP. Yeah. Don't care if you are a rocket scientist. Your readers won't follow your formulas for more than a line or two. Sorry. Trope this and move on.
4. SFF characters wanted: Straight white dudes only need apply - Have you noticed? Most SFF characters are straight white dudes. Because only white guys are stupid enough to get bitten by radioactive spiders? Or strap on a bunch of tech, some painted body armor and go swinging around Gothom dispensing vigilante justice? Or, you know, how only white guys with British accents ended up in outer space in Star Wars? CHANGING IT UP: If I have to explain this one, I will cut somebody.
5. Zombies - The undead are a big deal right now. Evil Dead. Walking Dead. Dawn of. Shawn of. So many Deads. Zombies at every turn. (Guilty - I did a zombie squirrel scene in a book because, c'mon. Zombie Squirrels, man!) Whether there's a rational explanation for zombies, a magical one, or no explanation at all, the undead ARE out to get you. Even in space - an argument can be made for Alien being a zombie equivalent because the critters, while alive, are so alien they may as well be the undead. They have the same hunger and the same persistence in hunting their prey. CHANGING IT UP: This is another question of WHY. Why zombies? Could your characters face the living? What is it about rotting corpses that furthers the story and character arcs in a way nothing else could? Again. 'It'd be cool and I want a cameo on The Walking Dead' probably isn't going to be sufficient to break you free of the trope trap.
6. Apocalypse - There are two kinds of Apocalypse trope: 1. The apocalypse as it is happening - the world is going to hell in a hand basket right now and my story follows that. Think disaster movies. 2. Post apocalypse - after the world has gone to hell in that hand basket. Planet of the Apes. Logan's Run. Mad Max. CHANGING IT UP: Okay. So 'apocalypse' does indicate that things aren't going so well for the human race - but you could chronicle the rebuild. The struggle to turn the apocalypse around. You can play around with what the actual apocalypse IS. Childhood's End by Arthur C. Clarke can be called an apocalyptic story - it does chronicle the end of the human race as we know it. But it isn't because of disease. Or natural disaster. Or the bomb. It's aliens who come to shepherd humanity into something Other. So many options for writing the merciless destruction of 7 billion souls...
7. Time Travel - Terminator. Star Trek - in just about every permutation of the franchise. In fact, there are so many time travel instances, there's a wiki page devoted to listing out the episodes and movies with time travel in them. In the Star Trek universe, time travel was such a thing, the writers finally invented time police to keep the time lines from being messed up. Given how easy it is to shoot oneself in the foot in a time travel (by creating a temporal paradox), time police would be handy in THIS universe. I give you the Terminator movies as evidence. CHANGING IT UP: No temporal paradoxes! Make sure MC actions in the past don't negate the entire plot. Don't go killing grandpa unless your daddy has already been conceived. Otherwise, you won't be born to go back in time to kill old granddad. You'll get tired of seeing this. But yeah. Why go anywhere in time? What purpose does it serve that can't be accommodated in the right here/right now of your story? If you have a specific answer to that, then more power to you. You've probably subverted the trope.
9. Bug-Eyed Monsters
10. Fairy Tales are REAL
Oh look. I left the last three blank. Because by now, you know what I'll say. Robots/AI - any Isaac Asimov book (there's someone who changed up a trope by inventing the three laws). War Games (remember that movie?) We all know that the robot/AI trope is about examining what it means to be human - and maybe to challenge where the line between sentient and merely cleverly programmed lies. Bug-Eyed Monsters - Scifi from the 50s and 60s featuring any creature out to predate the human race. Alien would totally count, except that the BEM trope requires that the monsters come to earth to get us. Total Cold War fears mirror. Fairy Tales as real - Once Upon a Time, Shrek, Ever After, Wicked
Point is tropes can be made to work for you. IF you're clear on why a trope is necessary to the fabric of your story. How do you do that? Dissect what you want that trope to say about your characters and your story. Why that trope? Why not another one? Could you reverse the trope or combine a couple of tropes into something newish that would heighten the story? How would that change what you're trying to say?
This is personal opinion only, but I suspect that tropes slide down the 'bad' side of story mountain when they're an unexamined, possibly lazy short-hand standing in for really understanding the point of a story. Conversely, I think that when tropes are applied consciously as tools used to ratchet tension, they can be elevated to something far more than trope.