Browser-based slideshows rendered with reveal.js.
I used to edit index.html files directly in a text editor. While emmet made that somewhat doable, I was constantly distracted from my content by the need to match opening and closing tags, nest divs appropriately, etc. Then I discovered how to use Pandoc to generate HTML slides, and things got a lot easier. (See this documentation also.) Now I write each slideshow as a Markdown document, which itself becomes a concise version of the presentation content.
Note that presentations with citations require the Pandoc filter pandoc-citeproc to be available as an executable on the path.