Not OP, but: e-mail client, calculator, calendar app, TODO list app, terminal app, file browsing app, invoicing app, Jupyer notebooks (org mode can do you better), Git client and - obviously - text editor with syntax highlighting.
Some people even replace their window manager with Emacs (see: EXWM), but I'm not ready for this just yet (I run stumpwm now, which is a tiling WM written in Common Lisp, so it's just another lispy environment with similar levels of live interop).
I'll bite. Name some things you believe are impossible. You may very well be right, but myself I yet haven't found a thing for which I wouldn't prefer Org Mode (except maybe that Github renders .ipynb files nicer than .org).
Org Mode can execute blocks of code in any language you can hook up to Emacs, correctly handling sessions if language supports them. Org Mode document itself can serve as a glue for exchanging data between different runtimes if you're using multiple different languages in a single document. Literate programming capabilities let you include other source blocks or even their results as code. Emacs can display images inline, and has some capability for UI widgets (though I haven't use it in org-mode context). The kind of Jupyter notebooks I've seen in the wild, I can reproduce in Org Mode with ease.
Well, according to my understanding, here are some things I do with Jupyter notebooks that org mode can't match: Dozens of inline interactive plots, including animations, 3d displays, generated SVG, embedded Javascript animations with widgets controlling them, proper formula formatting in code output and prose, etc. Things I have begun work towards include inline display of generated PDFs, and inline drawing widgets (including stylus pressure) that provide data for further computation and 3d display.
Simply not being browser-based means org mode has an incredibly steep uphill battle to even get close - the ecosystems Jupyter can tap into are vast (browser and native, language agnostic), and anything interactive is almost certain to trail behind.
I'm happy to be corrected, but I spent a while researching org mode's capabilities in this area earlier, and everything I found looked more primitive and clunky than what Python and Sage could do as long as 10 years ago.
I concede the point. I'm not aware how one could embed a webview in Emacs buffer, and without this you won't get animated/interactive plots.
My experience with Jupyter was limited to static plots so far (I did plenty of interactive work in ObservableHQ though), and Emacs can handle those well.
Some people even replace their window manager with Emacs (see: EXWM), but I'm not ready for this just yet (I run stumpwm now, which is a tiling WM written in Common Lisp, so it's just another lispy environment with similar levels of live interop).