The phrase "most old hat" means something that is outdated, obsolete or passe. Antonyms for this phrase would be words that represent the opposite of these qualities. Some possible antonyms for "most old hat" would include modern, trendy, fresh, innovative, newfangled, cutting-edge, hip or contemporary. These words refer to things that are up-to-date, relevant, and in sync with the latest trends and technology. In today's fast-paced and constantly changing world, being modern and innovative is crucial for success. Therefore, it makes sense to focus on the antonyms of "most old hat" to stay ahead of the curve and thrive in any field.