When we hear the expression "old chestnut," we often associate it with a well-worn idea or story that has lost its novelty. However, there are several antonyms for this phrase that suggest freshness, uniqueness, and innovation. Some possible antonyms include "newfangled concept," "original thought," "cutting-edge idea," "modern approach," "uncommon insight," and "fresh perspective." By using these phrases instead of "old chestnut," we can convey a sense of excitement, creativity, and originality in our language and ideas. So next time you want to express a new idea or approach, consider using one of these antonyms to make your message stand out.