Original Purpose: Mantelpiece clutter, proof of popularity.
Aha! Use: Gift tags. Last year's holiday and birthday cards may be too pretty to throw away, but they're probably not meaningful enough to keep. Cut out hearts, flowers, or any other whimsical illustration from the card's cover, avoiding handwritten notes on the opposite side, and stash them with your ribbons and wrapping paper.
Reward: It's not regifting; it's recycling.