Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Pine - A lightweight, modern macOS markdown editor written in Swift
Typora - A minimal Markdown reading & writing app.
THOUGHTS - An easy way to share your thoughts and feelings with friends
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.
Journal - Organize all your ideas