A Guice (pronounced "juice") developer primarily works with Google's lightweight dependency injection framework for Java. They use Guice to manage object creation, handle dependencies, implement modular programming, and improve code maintainability. They create reusable and interchangeable modules, manage life-cycles of objects, and ensure efficient unit testing. Guice developers also work with the framework's advanced features like custom scopes, binding annotations, just-in-time bindings, and provider methods. They must understand Java and object-oriented programming, and possess strong problem-solving skills. They continuously seek to optimize code, reduce complexity, and enhance system performance using Guice.