Manuskript - Open-source tool for writers.
Final Draft - Use your creative energy to focus on the content; let Final Draft take care of the style.
FocusWriter - FocusWriter is a fullscreen, distraction-free word processor designed to immerse you as much as...
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
Byword - The easy way to write Markdown and rich text on your Mac and iDevices
Trelby - The free, multiplatform, feature-rich screenwriting program!