If you regularly use candles, save your spent ones and use whatever wax is left to make one more usable franken-candle. All you need is a few basic items to ensure that leftover wax won't go to waste.
Candles always reach a certain point where most of the wax has gone and they can't really be used anymore. Bryson at do-it-yourself blog ManMade recommends gathering all of your spent candles, melting the wax down and creating your own new candle. Place your spent candles on a cookie sheet to bake at your oven's lowest temperature. While their wax is melting, hot glue a new wick to the bottom of a mason jar. Once the wax in the oven is all melted, pour each candle into the jar and wait for it to cool. Check out the complete guide at the link below.