What are the two possessions of which Della and Jim are most proud?

DELLa and Jim are most proud of their respective possessions: DELLa's beautiful long hair and Jim's prized pocket watch. These items hold deep sentimental value for each of them, symbolizing their love and personal sacrifices. In the story "The Gift of the Magi" by O. Henry, both characters ultimately sell their cherished possessions to buy gifts for each other, highlighting the theme of selfless love.