Your missing plugin(s)

I’ve scratched out a nice little business for myself creating custom plugins for small businesses. These are typically one-off plugins that serve a very specific need for that business in their particular industry. But I’m ready to try and make something for the public at large.

So my question for all you theme authors out there is: What plugins can’t you find? What key functionality is missing from the repository that you’d like to start including in your theme(s)?