1. For cold rain or snow, I carry a pair of large dishwashing gloves that I put on over my full finger gloves. They keep my hands warm and dry and they are cheap, very light weight and don't take up much space.
2. I wrap my duct tape around a small pencil so it doesn't take up much space or I wrap it around a section of my frame pump.
3. Guys, I save my first empty Gatorade bottle and keep it in the tent with me so I don't have to leave the tent in the middle of a cold night to relieve myself. It takes up a little space in the pannier, but it is very light weight to carry.
4. When I'm camping, I really like having a soft chair so I have one similar to this that utilizes my Thermarest sleeping pad. It is also lightweight (for a chair) and folds up nicely to strap on to my rear rack.
5. For a backup to a flashlight or headlamp in case they burn out, I carry one of those little promotional keylight mini flashlights. They are very small and light weight.