Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers
TaskPaper - Plain text to-do lists for Mac
Quest - Quest lets you create sophisticated text-based games, without having to program.
Microsoft To-Do - Task management tool