The phrase "most dime a dozen" means an item or phenomenon that is so common and abundant that it holds little value. Therefore, antonyms for this phrase might include words such as unique, rare, scarce, precious, and valuable. These words suggest something that is exceptional and highly prized or sought after, as opposed to widespread and easily accessible. For instance, an antique or bespoke item might be described as the opposite of "most dime a dozen" due to its rarity and uniqueness. Similarly, a highly skilled professional, such as a top surgeon or scientist, might be considered the opposite of someone who is "most dime a dozen" thanks to their specialized expertise and exceptional abilities.