1. Faster-Than-Light Space Travel
2. Magical Artificial Gravity Generator
Gravity. It allows plastic surgeon to make their Porsche payments, apples to fall, and drinking glasses to smash, and it is one of the greatest roadblocks to deep space travel to the stars. Our bodies were developed for operation on this planet that has gravity, and the effect of years without gravity could cause massive medical issues for our space trekkers. It the world of sci-fi, nearly every starship has some sort of soft-serve magical artificial gravity generator that works even when main power is knocked. Artificial gravity could be created using rotating sections, creating centrifugal generated 'gravity', and these ships would have be designed around this concept...just look at the USS Discovery's habitation decks from 2001: Space Odyssey. Even with rotating sections, only portions of the ship would have a gravity environment, and it would not be the same has back on terra firma.
3. No Inertia in Space Travel
4. Superluminal Interstellar Communications
5. Crowned Space
6. Instant (just add water!) Communication with Alien Species
Every week on Star Trek or Stargate, our intrepid heroes teleport off to new worlds that look like back-lot or Canada and met bumpy fore-headed aliens that speak prefect English, or our heroes iphone universal translator app works perfectly. The sad truth is that communication with an intelligent alien species that evolved on a completely different world than us would be a long, painfully process, requiring experts in the field of linguistics to live with these aliens. After all, when we sent probes out into deep space, those golden discs used symbols, math, and sounds to communicate. I realize that sci-fi stories have to use the equivalent of the microwave dinner to accelerate the plot and make for the vision of populated galactic community, but sometimes it takes away from the 'alieness' of the creatures, because we can talk to them instantly. One of the my favorite sci-fi books about this subject is Mary Doria Russell's the Sparrow.
7. Rise the Shields!
8. Starship Appearance
9. No Time Dilation
Time dilation is one of those an inconvenient truths of physics that could make traveling to distance stars incredibly difficult for future generations. To deal with this problem, the vast majority of science fiction pretends it doesn't exist or that there is an magical hyperspace corridor that cancels out the effects of time dilation. For an author/creator to include time dilation means that critical points of the plot will focus on this factor, instead of zipping from star-to-star while getting synthohol at Ten-Forward. Because of the indoctrination that soft-serve sci-fi has programmed into the collective consciousnesses, it is very difficult to reconcile worlds like Trek and Wars with the time dilation in the real-world. Ugh. FWS has discussed this space phenomenon to death on many blogposts and will continue to discuss it...sorry in advance for that.
10. Sheath In Space