I've always wanted a clipboard/paste manager - with history - like this, that would allow me to copy, manipulate, and paste or share that data to another application.
I don't know how this would look, but even the ability to pop open my paste manager and look at the copied contents, filter it, or split the text, or (silly stuff) convert text to emoji'fied content, or take a screenshot of that (text to bitmap), and create a new entry within the paste manager. For some of my friends it would be awesome to have a hex editor in there.
Perhaps there are 2 focuses: Isolating what is copied from applications until the user chooses to expose it, and the history function. Being able to send it to another app for manipulation and pulling it back is a 2nd responsibility. It would be /suave/ to have this all in the same GUI brought up by the compositor, though.