Recently I've been using iAPresenter [1], which lets you build presentations using Markdown. I actually use it to create branded PDF proposals for clients and it makes life much easier than having to use Google Slides, Keynote or Powerpoint. The philosophy of iAPresenter (and iAWriter) is more about minimizing distractions, but the side effect is that you end up in control of your files too.
Another tangential example is Dropshare [2], a Mac app for sharing files. You can plug in your own backend (S3, Backblaze etc.) and domain and have your own branded file sharing service, while "controlling" your files (although they are obviously still hosted on a 3rd party server)