A little while ago, I grouped unicorns and other successful companies by business model. What emerged was fascinating. Over the last ten years or so, there were only 18 business model categories that have produced winning Internet companies.
I think these business models can produce scalable, defensible companies and that is why these categories win.
Apart from existing business models, I am also interested in entrepreneurs inventing new ones. Looking back, I think you tend to find that new business models are an evolution of existing ones. For example: classifieds -> search. content -> social interaction tools. software -> SAAS.