Sawyer PointOne Portable Water Filter | $20 | Amazon
The concept is similar to LifeStraw—dirty water from a pond or stream goes in, drinkable water comes out—except that the Sawyer can be cleaned and reused basically indefinitely, whereas the LifeStraw has a lifespan. The PointOne can also screw onto a standard water bottle or the included 32 oz. squeeze pouch, so you don’t have to hunch over a body of water to take a drink. I’ve tested it myself, and here I am, not dead!