Strapi is my go-to open-source headless CMS for projects that require a high level of customization while keeping as open-source as possible. Strapi provides a visual interface for creating and managing content models, giving developers the ability to define their own data structures and content types. This allows for highly customized and structured content management tailored to specific project needs.

Strapi's open-source nature, headless architecture, customizable content models, RESTful and GraphQL APIs, user-friendly interface, plugin ecosystem, role-based access control, scalability, and active community make it a powerful and flexible CMS for building content-rich applications.