The Alloy of Law (Mistborn, #4)
Editing my previous review now that I've thought back on it several times. This book was tons of fun, and I still giggle out loud when I think of a few of the one-liners. I also caught (I think) one subtle kandra appearance towards the end of the book, and I'd love to know more about that. Not to mention the other huge scene right towards the end.
I know this was only meant to be a writing exercise, but I'd love to read more stories with these characters.