What I have here is a kit that I carry when I am with a group. It has in it everything that I would need to take care of myself and another person or a couple people in a situation where we were stuck out for a long time, and we had to deal with taking care of ourselves in a wilderness environment.
Some of the things that I have in here, you'll notice it's in a dry or dryish bag. The dry bag itself serves several purposes. It keeps the ingredients inside dry, relatively, but it also serves in a pinch as a water container. It serves as a pot to cook in. I can collect food in here. So the bag itself is an essential part of the kit.
Inside the bag, everything is in Ziploc bags which also, again I can collect water in, I can cook in. I have garbage bags, candle, and a lighter. Garbage bags can serve as a shelter. They can also serve with the candle as an emergency warm up kit so I can take care of somebody that's hypothermic or if I'm cold myself, I can't really function very well as far as getting a fire started or anything like that, this is a way to warm up.
I also have, for my own comfort and convenience, a little toilet paper and a wet wipe. Not necessary for survival, but keeps you less gross in the back country.