Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Boostnote - Boostnote is an open-source note-taking app.
Textile - Textile is a lightweight markup language originally developed by Dean Allen and billed as a...
Standard Notes - A safe place for your notes, thoughts, and life's work
Typora - A minimal Markdown reading & writing app.