Typora - A minimal Markdown reading & writing app.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.
Invision - Prototyping and collaboration for design teams
MarkText.app - Mark Text is a Markdown editor for Mac, Windows and Linux.
Sketch - Professional digital design for Mac.