IMHO: I don’t claim the universal truth / AFAIK: I write to the best of my knowledge
Software
Development
Editors & IDE’S
Emacs: The first really IDE-like eidtor i encountered and learned to use, available on virtually any platform one could think of, and (in my opinion) still going strong. org-mode rulez!
Notepad++: For many years now the fast editor on Windows for simple text editing for me.
Productivity
Logseq: For some years now my number one note taking app, replaced Emacs/org-mode and MS OneNote in my day-to-day work.
Sumatra PDF: Free and fast view for PDF files (and other formats)