Castoffs refer to items that have been discarded or rejected. However, there are many antonyms for castoffs that describe items that are treasured or valued. These antonyms include heirlooms, keepsakes, mementos, souvenirs, and relics. Heirlooms are valuable items that are passed down through generations and are treasured for their sentimental and historical significance. Keepsakes are cherished items that hold special meaning and are kept as a reminder of a particular person or event. Mementos and souvenirs are items that are kept as a reminder of a place or experience, and relics are historical artifacts that have been preserved for their cultural significance. These antonyms for castoffs remind us that some things are meant to be cherished and valued, not discarded.