i'm assuming that if you're 'backpacking' you're not driving from place to place.
at least one candle. sometimes you want flame not just torch light. and the wax can also come in useful if you're trying to light a fire with damp stuff (paraffin wax is the same stuff used to make 'fire lighters'. and a lighter.
sharp knife of some kind.
needle and thread/ dental floss
a fabric pillow case can be really useful - you can stuff it with clothes and use it as a pillow - or use it as a bag to carry laundry etc around
paper maps - don't rely on some gps gadget or your phone to always work
at least one pair of socks that are always kept dry/ in a waterproof bag. so that if you get soaked, once you've got the tent up you can get/ keep your feet cosy
shee pee devices can be really useful, depending on where you are. and some toilet paper that isn't a wet wipe. small (tough plastic is lightest) garden trowel, if you're digging your own toilet holes!
plastic basin/ large bowl - multiple uses, incl as a makeshift fridge with some cold water in it, very light to carry