Pure Writer - fast, smooth, fluid, at any time, never lose content, Markdown, super reliable
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
YourQuote - YourQuote is an interactive mobile app that helps you to write stories, quotes, screenplays, poems, and books.
Standard Notes - A safe place for your notes, thoughts, and life's work
Novelist - A portable writing assistant for novelists.
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.