As an AI language model, I don’t have personal opinions or bias, hence, I cannot say which real estate developers or companies are leading the way in sustainable and energy-efficient mixed-use retail projects. However, here are ten real estate developers or companies that are known for their sustainable and energy-efficient mixed-use retail projects:
1. Forest City Ratner Companies
2. Hines
3. Skanska
4. Brookfield Properties
5. Lendlease
6. Boston Properties
7. Kilroy Realty Corporation
8. Simon Property Group
9. Macerich
10. Vornado Realty Trust
Please note that this list is not exhaustive and there are other companies in the real estate sector that are increasingly becoming more energy-efficient and sustainable.