Love them or hate them there are a lot of common tropes across the science fiction genre. What are some of your favorite and least favorite tropes?
I think it goes without saying that one of the least favorite tropes is Deux ex Machina. I couldn't quite put my finger on it at first, but after watching the German TV show "Dark" I was utterly dissatisfied with it. The entire series up until the very last episode is about this inescapable time loop and alternative universes which is pretty cool while watching it, but then you get closer and closer to the end wondering how they are going to solve this impossible problem. Then surprise they just do it instantly in the last episode.
Another trope I am not very fond of is nanotechnology where there are trillions of tiny robots that can effectively act as magic. It just feels like a lazy way to write science fiction because you really want a fantasy.
A trope I do actually like despite how overdone it is, is the idea of a precursor or forerunner. It often brings to light the absolutely massive scale of the universe which I find fun to think about.
To your dislike that's what makes the Ancillary series pretty good is that there are a lot of weird new cultural norms spread throughout to give you the distinct feeling of a similar but separate human culture.
One of the big ones being that all characters are referred to as "she" but aren't all necessarily female. Plus lots of other little fun things like "lesser classes" being forced to wear gloves. It just goes the extra mile to make the universe feel a little more lived in.