My Sci-Fi pet peeves?
#1: United Mankind.

I doubt it. My take on this in The Swarm War is that mankind splintered post-interstellar exploration as the various nations made a free-for-all territory grab. I think we're too diverse with our own agendas to come up with anything like the UFP, TC or EA.
#2: No sooner do we leave our own star system than we run into 45 alien species. Okay, we might, but I doubt it. At most we'd run into perhaps three, and they might not be interstellar capable.
The sublight lasers have already been mentioned, so I'll leave that out.
What else........hmm...........oh yes:
#3: Mankind, no sooner have we developed interstellar travel and advanced technology, suddenly become American. What happened to every other nationality? (This pet peeve is remedied in The Swarm War. The Karran Imperium is 90% British in origin with the remainder made up of Japan, Germany and a few others).
#4: Timescale. How in the name of all that is holy do we have a vast sphere of influence by the 23rd century? At best we're looking at the back end of this millennium, assuming interstellar technology is developed and made cost effective within the next century.
#5: A vast supply of inhabited worlds in some franchises. Okay, our knowledge of the galaxy is slim at the moment, but seriously, will practically every star system contain an inhabited world with a population of 5 billion of whatever race holds sway over that region of space?
Can't think of anything else right now.....