Buzz feed lists a lot of ways to use crayons and a hair dryer for a really neat effect but the one that's most different is using up all of those little crayon pieces to create something new. Kids will have as much fun smashing up the crayons and designing them on the page as they will melting them.
Good for ages 5 and up.
Get the instructions here:
http://www.buzzfeed.com/donnad/creative-ways-to-create-melted-crayon-art
Growing a jeweled rose uses crayon shavings as well, but instead of a hair dryer, she leaves her canvas out in the sun and answers the question what happens when crayons are left out in the sun?
Get the instructions here:
http://www.growingajeweledrose.com/2013/08/paint-and-play-crayon-art.html