Ziploc bag
From Cookipedia
Ziploc is a brand of reusable, re-sealable zipper storage bags and containers originally developed and test marketed by The Dow Chemical Company in 1968, and now produced by S. C. Johnson & Son. The plastic bags and containers come in different sizes for use with different products. The brand offers sandwich bags, snack bags and other bags for various purposes.
They are useful for to marinating food, evenly coating food with other ingredients as a storage medium, however, I personally prefer to use Lock & Lock boxes for all of these uses as they can be used an unlimited number of times.