Original Purpose: Food storage.
Aha! Use: Packing. No bubble wrap? Slip a straw in a nearly closed Ziploc bag and inflate. Remove straw, seal, and cushion cargo. Wrap delicate items with newspaper first. (And heirloom china should wait for that bubble wrap.)
Reward: Girl Scout pride.
Other Use: As a pastry bag; Fill with icing, zip shut, snip off a corner, and squeeze.