If you're looking for an AI-powered tool to help with creative writing, Sudowrite is a great option. It taps into large language models like GPT-3 and GPT-4 to help with all aspects of the writing process, from idea generation to editing and refinement. Sudowrite has a range of tools like Brainstorm, Describe, and Visualize to help you get ideas and refine your writing style. It also has more practical tools like full-screen focus mode and project organization, so it's a good all-purpose writing tool.
Another good option is NovelAI, a subscription-based service geared specifically for authorship and storytelling. It includes tools like text adventure modules for interactive fiction, a customizable editor, and a lorebook for keeping track of world-building details. NovelAI's AI is trained to write in your style, so it's a good option for fiction writers looking to explore different narrative styles and formats.
If you're looking for a more productivity-focused tool, you might like Rytr, a free AI writing assistant with a range of tools. That includes AI autocomplete text, grammar checking, and content optimization tools. Rytr is geared for writers who need to create and edit content quickly, with options for different writing styles and tones. It also has a plagiarism checker and SEO meta title generator, so it's good for writers who want to improve productivity and ensure their content is good.