I'm boring and I really like rotating megastructures. I think what I find fascinating is they're feasible for us to make IRL if we somehow figure out refining on the moon and mass drivers (ignoring the economics too lol) since they use conventional materials even for relatively large ones.

Everyone is always focused on terraforming or colonizing distant planets. A rotating habitat is engineered to be exactly what we need better than any planet we can colonize.

Life on Mars would be demonstrably worse. You need to bury your habs under meters of regolith to not kill your colonists from radiation. Going outside is a space walk with a laundry list of items you need to attend to with little to no time to enjoy being outdoors (you're in a suit regardless which means it sucks to some extent no matter what)

A rotating Hab means you can live much closer to how you live on Earth

Just give me neon lights in the rain and I'm already happy.

I love the dying earth trope. Its earth, but millions if not billions of years after present day. I love thinking about what the humanity of today might leave to be discovered by whatever comes next. I think the first real exposure I had to it in media was that Artificial Intelligence movie from 2001. Its been around in fiction a lot longer, but that was the first time I really "got" it. Its so neat to me to think about how an alien (or a distantly removed human) might interpret the present day.

In Doctor who spin-off media there exists a voodoo time-travelling cult called faction paradox. They wear bones and skulls. To obtain these they find a species, hunt them, then go back in time and prevent that species from ever having existed in the first place

So they’re wearing the real bones of creatures who never evolved and never existed

That’s pretty cool

Elite Dangerous's Frame Shift Drive having both modes of operation with the standard Alcubierre drive which allows you to do FTL by contracting spacetime around your ship (hence frame shift) or near instant system travel by creating a wormhole to travel through.

The catch is that while supercruise has been around for a long time and works just as you expect, the wormhole hyperjump is new reverse engineered tech by captured Thargoid technology.

The drive uses mass to guide the ship to the destination, meaning it can only work by locking onto primary stars of a system. You can only make wormhole jumps between systems but must use supercruise to get to where you actually need within the system.

Also that mass affects its operation:

Being close to any mass will affect the FSD charge time. While being next to a heavier ship will merely make it charge slower, the FSD will get mass-locked should the ship be next to something extremely massive (station, asteroid field, etc.) and will be unable to charge at all.

The evolved species in Adrian Tchaikovsky's "children of time" series. So much thought and detail went into them and he's a fantastically descriptive storyteller. His command of language is superb.

I don't want to spoiler too much beyond that but it's easily my favourite series.

"We're going on an adventure"

A couple from from Douglas Adams' Hitchhiker's Guide to the Galaxy series have always stood out to me:

The Infinite Improbability Drive is used to propel a spaceship by means of increasing improbability to infinity. It ramps up improbability at your departure point until you are literally everywhere at once since everything is possible, then ramps it back down leaving you at your destination. The offshoot being a whole lot of highly improbable other things happen in the vicinity.

The Total Perspective Vortex is a machine that upon entering gives one a perfect sense of perspective of the entirety of existence (which it derives from a piece of cake.) No one emerges sane. It was invented by a guy to get his wife to stop nagging him.

I really like sci fi settings where there is one major leap of physics that has ramifications across the rest of the setting.

Mass Effect is my prime example with the discovery of mass effect fields that allow the manipulation of how much mass things have. This is the basis for local interstellar travel after using a mass relay, as the mass of the ship is reduced for acceleration greater than the speed of light. Artificial gravity is created by increasing the mass of the floor. Guns work by electromagnetically accelerating bullets through a reduced mass field for greater acceleration, while shields work by emitting repulsive mass effect fields.

In The Expanse, the only technological breakthrough that doesn’t feel like a natural extension of modern technology is the Epstein Drive. The only thing it does is make propulsion engines fuel efficient enough that they can burn nonstop between destinations, which allows a ship to constantly accelerate to its destination instead of reaching a maximum velocity then floating the rest of the way there. It cuts down travel times between planets from months/years to weeks, and allows the society presented to exist.

You might be interested in browsing through this site:

https://projectrho.com/public_html/rocket/

It talks about a lot of sci fi tropes from a hard science perspective, and goes over FTL specifically:

https://www.projectrho.com/public_html/rocket/fasterlight.php

It's kind of a downer site in some respects because it does a lot of "here's why your favorite sci fi series is unrealistic", but in that discussion there's a lot of looking at interesting tropes and concepts. There's also a good explainer for FTL specifically here:

https://www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-time-travel

A tardis from Dr who. It's a living spaceship + time machine.

It also has some insane features like:

1. It's bigger on the inside. In fact it has infinite rooms and storage.

2. It also has access to all knowledge across time.

3. It can instantly translate all languages telepathically. So everything you hear and see will automagically be in your language.

4. It can take any form physically. On both the inside and outside. It has a chameleon circuit which makes it blend perfectly into the surroundings.

It's said that it's destiny to be chosen by a tardis. It reads your thoughts and takes you where you want to go or where you are needed.

Anne Leckie’s Translators. Aliens so alien that the only way we can have any shred of common ground is by them taking a few humans and rebuilding them specifically to be their ambassadors, with interesting results.

The Uplift Series is a gem. Copied directly from Wiki because it's succinct yet thorough:

The Five Galaxies are filled with alien races, all of whom were "uplifted" into sentience by another race through the use of directed breeding. As "payment" for being made sentient, the uplifted races are subservient to their uplifters for a period of time. All existing races have reached sentience through this process, and follow a common evolution in which the races become free of their uplifters, enter a period of independent power, and then fade and eventually disappear.

The arrival of a human ship at a populated star upsets the established races as humanity reached sentience on their own. This had been believed to be impossible, nothing of the sort is known in the eons-old galactic library. This leads to great arguments among the alien powers. Humanity begins to uplift other species on Earth, including chimpanzees and dolphins, but does not demand subservience.

my favorite trope that i dont see enough of in movies is realistic galactic travel and all the tech that would require.. travel to another star system.. usually multi-generational attempts. feels like there is a lot of this in books.

you often see a brief glimpse, or some hand waiving with hibernation techniques. not much feels real.

This is a bit of a general one, but I have a fondness for very large space structures. A number of my favorite scifi stories take the premise of "exploring a (usually abandoned or tech-regressed) alien megastructure".

Dyson spheres and ringworlds and stellar engines and the like are the obvious candidates, but honestly I like smaller (but still huge) ideas like oneill cylinder colonies just as much, because what I like in them is a function of both size and how close to understood physics they follow, and the latter tend to be easier to make plausible.

There's a certain sense of inspiration that comes of someone describing something almost incomprehensibly huge, explaining that it is designed by intelligent entities, and then justifying it with enough real science as to convince you that something at least somewhat like it really could exist, someday, or maybe already does somewhere out in the vastness of the universe.

I can't remember what book it came from, maybe one of Peter F. Hamiltons, but portals was a thing. So naturally the superrich had houses where rooms were not on the same planet. The doors between the rooms looked normal, but was portals to the next room somewhere else.

Especially the toilet tickled me. That was situated on an open raft on a deserted ocean covered planet.

Speaking of Alastair Reynolds, concept of Pattern Jugglers - benign algae-like pools that oscillate in strange image-like patterns and can physically connect, read, and modify human brains. A person entering the Pattern Juggler could experience someone else's life, temporarily gain skills or knowledge, or... die.

In Ursula LeGuin's Left Hand Of Darkness, I love the idea of society without war. There is still violence and murder, but fighting on someone else's behalf must be viewed as incredibly absurd and unacceptable.

Department Of Truth comics are based around the idea "what if what we believe becomes true?". So cryptids, UFOs, and conspiracies exist because enough people believe in them.

The depth and mechanics of Orogenes in N.K. Jemisin's Fifth Season / Broken Earth. It's not just "I cast frost", it's heat and energy manipulation, with sense, direction, and geometry.

I cant pick just one but since you mentioned Conjoiner drives (rev space is my all time favorite series) I would say that the cryoarithmetic engine is super crazy. They popped up in Star Sector as well, I'm guessing as one of the many SF references in that game. If you like good SF games that have a ton of depth, check Star Sector out. You can purchase it from the website directly, it doesnt mess around with third party bs or drm software or anything.

One thing that absolutely stuck with me as an idea was the plot premise of the short story The Road Not Taken by Harry Turtledove. In this story not only is FTL travel by gravity manipulation possible, but also very very easy to discover. It's so easy that many aliens discovered it early on and then their progress on technology is basically halted. So humankind is a very advanced civilization because we never discovered FTL travel which led to our advanced technology. Then one day one of the "prehistoric" alien races try to conquer the earth and can't grasp what they're up against.

In my own made up worlds I often imagine FTL works by moving between the 2nd and 3rd dimensions. 3D is “flattened” in such a way that point A (where you start) and point B (where you want to be) are at the same point of the now 2D universe. During the transition back to 3D, points A and B go back to their original positions, but you are now at point B.

Mine would be "The RiverWorld" novels by Philip José Farmer...

In Michael Crichton's Timeline, they send people back in time hundreds of years until they push a button to return, except they don't. The time travel has something to do with alternate timelines, so in theory there could be countless versions of them travelling back and forth in alternate universes or alternate realities or however you want to think of it.

The invention of time travel in our universe only got as far as figuring out how to send people back, but they never figured out how to return them to the present. Coincidentally a virtually identical alternate universe figured it out but they get sent to our universe on the way back to the present.

So every time we send someone back, we essentially kill them and in return we receive an alternate version of them that's so close to identical it's virtually the same as the original person. And for every person we get back, another universe loses that person forever. The organisation doing the time travel secretly know this is happening, but it works and it's cheaper then finishing the invention of time travel.