If what you are looking for is a fast and inexpensive emergency water treatment, iodine is a time-tested solution. Unlike all pump-filters with the exception of the First Need XL, iodine treats viruses. However, iodine does not treat for the cyst Cryptosporidium, while pump filters and chlorine dioxide treatments such as Katadyn Micropur Purification do. Potable Aqua Iodine Tablets and Taste Neutralizer tablets are small, hardly weigh anything, and are simple to use, so they are convenient to carry with you. One drawback to a hiker on the move is that iodine takes 30 minutes to properly sterilize water, which is one of the longest treatment times in this review.
According to Potable Aqua, "Potable Aqua is intended only for the emergency disinfection of water and should not be used in any other way." Iodine should not be ingested continuously over extended periods of time, so if you plan to go on a long trip or will be treating water frequently, a filter method or a UV light method like the SteriPEN Journey LCD would be comparatively lightweight options to consider.