Final Draft - Use your creative energy to focus on the content; let Final Draft take care of the style.
YourQuote - YourQuote is an interactive mobile app that helps you to write stories, quotes, screenplays, poems, and books.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
JotterPad - JotterPad Writer for Android — Turn your thoughts into text. Go about your creative writing without distractions, write to your hearts content...
Trelby - The free, multiplatform, feature-rich screenwriting program!
Novelist - A portable writing assistant for novelists.