After reading around, I have to pick Cohort's "Do Sirens Sing for Saxony" (available here:
http://forum.paradoxplaza.com/forum/showthread.php?t=304903)
The central conceit is that there is a secret diary passed from advisor to advisor, documenting the happenings of the realm over generations. So I'm really giving the award for the sum total of characters! What I really like is how the advisor's personality sometimes pushes to the fore (for instance really lambasting a bad King), or sometimes barely peeks through with a carefully-chosen word (perhaps the use of "heretical" to describe a certain set of enemies), like a minimalist Chinese painting ... use your brushstrokes wisely, for you do not get many.
Congratulations Cohort!
Ak