I bring a lot of stuff, really. I try to plan for the worst case scenario of being stuck out overnight. So I bring firestarters (lighter/tinder) since fire can keep me warm

a small pot, (aluminum can would work), since I can always boil water on the fire.

chlorine tabs, because boiling is annoying, and they're light

a poncho tarp with lines and stakes, since this is more than adequate as a shelter, and serves as rain gear too.

a couple plastic bags, which work as VB insulation, or could carry water in a pinch. Also some ziplocs, one for my cellphone in case it rains. produce bags for my feet/hands.

usually a space blanket if I have room. The only thing that's likely to kill you overnight is hypothermia.

Really I carry a lot of what I would for an overnight, minus the sleeping bag and primary shelter.