Falcon - Ultraportable 2-in-1 Laptop
MacDown - MacDown is an open source Markdown editor for OS X, released under the MIT License.
NotePlan - Make plans inside an individual markdown note for every day in your calendar. Use it as a journal for your daily tasks and plan todos in advance. For Mac, iPhone and iPad.
iA Writer - Minimal Design, Maximum Focus
Loose Leaves for Mac - Instantly share what you write in Markdown
MWeb - Pro Markdown writing, note taking and static blog generator