The phrase "most rinky-dink" is colloquial and refers to something that is cheap or shoddy in quality. Antonyms for this phrase could be high-end, luxurious, or top-notch, describing something with the highest quality, design, or performance. Other antonyms could include words like sophisticated, refined, or expertly crafted referring to a product or service that is expertly or skillfully made. Another set of antonyms could be valuable, exclusive, or prestigious which signify that the item is highly prized or regarded. Finally, antonyms could be solid, dependable, or durable that suggest that the item is reliable and built to last.