I've mentioned this before, but I'd love to have a note taking app as convenient as EverNote, but that lets me insert code cells a la Jupyter notebook. I can barely think without Jupyter any more. Maybe that's not a good thing, but it's sure handy.
Jupyter notebooks are great for capturing thought process and showing intermediate state of whatever it is you're doing, which means coming back to them even years later it's a lot easier to recall your own thoughts and not have to reverse engineer a monolithic block of code.
Jupyter has helped me take notes when I need to "think" quantitatively, and be able to look at answers quickly, plus maintain a record that I can read later on.