Any tips/ideas for re-purposing leftover candle wax? Thinking of making new candles out of them ?

I have made new candles out of old ones many times. There are various methods and how-to videos online. You can buy spools of wick and candle molds in craft stores. For tapers or birthday candles, I dip the wick in melted wax several times. I usually have a lot of glass jars from old candles, so I put in a new wick and add more melted wax. I anchor the wick at the bottom with something like a piece of tinfoil or a button. Adding the melted wax in layers, letting them cool a bit each time, also helps keep the wick in the center. I've even used tin cans, tin foil, teacups and paper cups to make new candles.  

Just melting the wax on the stove will smell as good as a lighted candle, too. I put the extra wax in a clean soup can or a glass jar, inside a pot of water set on the lowest setting. 

I've also used old candle wax to make fire starters, for fireplaces or campfires. I used cardboard egg cartons (that I had on hand anyway), and stuffed dryer lint into the egg pockets, then poured the melted wax over everything and allowed to cool. They can be broken apart and used individually, placed in different spots under the wood. The egg carton and lint act like a wick, for lighting, and the melted wax becomes fuel that keeps the wood burning. 

Easier still. Put the residue wax in a tart warmer. 

I put the candle jar in my freezer, brake up the wax and store it in a baggie.  I put in my tart warmer to melt as needed,