There are many contenders from "Turnabout Intruder," "Spock's Brain" and "The Omega Glory." But what really gets on my tits are Dramatic Moments when the ship has just completed an adventure, helm asks for a new heading... and the Captain stares mistily off into the distance and Says Some Bullsh*t.
For this trope, I couldn't quite say whether Kirk's "Second star to the right... and straight on 'til morning" or Picard's "Let's see what's out there!" is worse. I think the first one, though. (Oh wait... The Motion Picture. "Out there... Thataway!" That's the winner.)