Final Draft - Use your creative energy to focus on the content; let Final Draft take care of the style.
Microsoft Word - Microsoft Word is a commercial word document processor for Windows.
Celtx - Celtx is a scriptwriting software platform with applications in a wide range of mediums but that specializes in helping screenwriters.
LibreOffice - Writer - Open-source cross-platform word processor.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Apache OpenOffice Writer - Open-source word processor of the Apache OpenOffice suite.