A variation on the core Archives widget where it is like a yearly list in addition to the months of the current year.
Order a specific category by date, the rest alphabetically.
Change the recovery mode email address to which the fatal error emails are sent to, instead of bothering and potentially confusing the site admin.
Add a CTA on the Essence Pro hero image on inner pages (i.e. not on home page).
With two defines and a plugin you can work on a staging site without editing the database or copying uploads.
A demo on how to internationalize, localize (and test) your WordPress code.