A few small things. One is either a second mini-Bic or a book of paper matches. I also carry a few of those REI Stormproof matches for emergencies along with a little fire starter, although i rarely, if ever, build a fire. I suspect that Jack London's "To Build a Fire" is in the minds of many of us! The second is backup for my water filter, in the form of two days' worth of Katadyn Micropur. The third is several large safety pins--in addition to first aid (pin sleeve to shirt to make an arm sling), they also can substitute for a broken zipper or missing buttons (when I was a kid, safety pins were known as "Wyoming buttons.") The fourth is backup sunglasses, the ones the eye doc gives you when he dilates your eyes. Mine are a wraparound piece of film, and would be useful underneath my regular sunglasses (which don't have side protection) if I were on a snowfield. Finally, if it looks like a soggy trip with not much drying opportunity, I'll take a third pair of socks.
Wearing all my clothing at once and wrapped up in my tent, I could survive a cold wet night if the tent blew down/ripped and my sleeping bag got soaked. I probably wouldn't be comfortable, but I'd survive! However, that's not taking anything but my normal clothing and gear.
Just thought of another one--around my neck on a cord, with compass and whistle, is one of those little pinch mini-LED lights. It has saved my bacon a few times when I couldn't find my headlamp in the dark (one time my dog was sleeping on it!).