Cooking This is the easiest category. There are many clever, lightweight stoves on the market. Cooksets are also uncomplicated. Any serious outdoors store will have a nice selection. Non stick surfaces are a good idea.
Water treatment is an interesting issue.
Basically, there are not many places on earth where you can trust the water. But most filtration systems are bulky and tedious. We treat water in our Nalgene water bottles. The first pill is iodine, which kills the nasties, and the second pill is ascorbic acid, which removes the taste of iodine. The two little bottles weigh 3 ounces, and they have kept us healthy in some scary places.