LightPaper - Admired by thousands, LightPaper is a powerful markdown editor with features such as Multi-Tabs, Folder Navigator, Distraction Free Mode, Quick Open, Live Preview, Full GFM Support, Math rendering etc.
Caret - Better Markdown Editor for Mac / Windows / Linux
Markdown Live Preview - Stop guessing about your Markdown formatting 📝
Typora - A minimal Markdown reading & writing app.
Iceberg Editor - A beautiful markdown editor for WordPress.
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.