There are many ways you can repurpose your candle jars!
Either pop in the freezer for 10 minutes to chip out the residual wax or the "oven method" on low (250°) until melted.
Then wipe clean with a paper towel and wash with hot, soapy water.
Here are a few examples:
Memories in a Jar: sand and shells from a special vacation
Mini Terrarium: sand, aquarium charcoal, some good dirt + a cactus
Cotton ball storage, make-up brushes, coins...The possibilities are endless!