You raise an essential point about the value of digital currencies being derived from their market presence and usability in circulation. In terms of recommending a digital currency that aligns with this criteria, one notable example is Bitcoin (BTC). Bitcoin has established itself as a widely recognized cryptocurrency with a substantial market and increasing acceptance as a medium of exchange. Its decentralized nature and limited supply contribute to its value proposition. However, it's important to note that the cryptocurrency market is dynamic, and thorough research is necessary to evaluate specific projects and their potential for adoption and real-world use. Factors such as transaction speed, scalability, governance, and partnerships play a crucial role in determining a digital currency's viability as a widely used medium of exchange. Stay informed, explore various projects, and consider their technological advancements and real-world applications to identify potential currencies that align with your criteria.