Old jeans have been used for many years for quilts. They are absolutely the very best for picnic quilts, for kids who love to play indians and make tipis with them, and they will last for years and years.
They WILL be heavy, don't need much if any batting, but if you live in a cold country then you can make a good one that kids and grownups will love for the warmth. And dogs and cats can sleep on them too, with not much chance of runs from sharp claws.