Powerful knowledge base that works on top of a local folder of plain text Markdown files.
Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features.
Vim ("Vi IMproved") is an advanced text editor that allows syntax highlighting, word completion and has a huge amount of contributed content. It also has a GUI version called GVim.
Typora will give you a seamless experience as both a reader and a writer. It removes the preview window, mode switcher, syntax symbols of markdown source code, and all other unnecessary distractions.
Zulip is a group chat app in which messages are threaded by topic, helping you have long-running, organized conversations.
Plain text notepad with markdown support and todo list manager for Linux, Mac OS X and Windows, that works together with the notes application of ownCloud.
Pandoc is a Haskell library for converting from one markup format to another, and a command-line tool that uses this library.
Difftastic is a diff tool that compares files based on their syntax. It supports over 20 programming languages and when it works, it's fantastic.