This is a stretch...but today U is for the Unusual or the Unique.
In all my stories, I try to come up with things that people aren't used to, and if it's a familiar idea, I feel like you want to desensitize people to the familiarity of it. I think this is the goal of every author.
With my pirates, I didn't want a stereotypical world where pirates were just barbaric and had no sense of law. In my books, they do--yes, there are some rogue pirates who disobey and give the pirates a bad name (although, mostly, the Privateers do a good job of giving all pirates a bad name) lol. I also wanted my map and my world to have a different feel. I felt if they were mostly islands, it would seem like a pirate-oriented community anyway.
Does that make sense?
Then I wanted to throw Elves in the mix. Mostly because I love them, and Elves are like ninjas anyway. SO then I could have a ninja-pirate-elf and be awesomeness.
So what do you feel is unique about your novel? :D