Stocking Stuffer #4 - a Life Straw
The Life Straw was one of my first prepper pick ups several years ago - this light-weight piece of kit insures you can have access to pure drinking water in every situation. Disadvantage is that there is no way to store purified water (so you are limited to getting water only from source to source) but at $20 or less (Amazon is running a special until 9 Dec 30% off), this makes a perfect stocking stuffer.
While I recommend you consider one of our Life Saver products for a more robust solution, they are a little too big for the stocking. But just in case you want to amp up your loved ones prep: