Good topic...
Starting with the sunglasses, watching the "on thin ice " TV series (race to the South Pole) I noticed that one of the guys had 3 different types os sunglasses/goggles, the other two had (at least) 2 each.
Snow blindness is not fun neither that unusual ...

I carry two Mini Bics except when using a light Kovea stove that has a reliable (so far) piezo ignition, then I have one.
No matches or magnesium sticks, but have some petroleum jelly impregnated cotton balls to start a fire if I need too.
Always have 3 pairs of socks. Two thick ones and a Coolmax type for bed. In camp if wet (or with wet shoes) I wear the thin socks with a bread bag (plastic bag) over them to keep them dry and clean.
(so I carry 4 plastic bread bags, 2 as a backup or for others)
Always have two short sleeve merino tops. One for day the other for camp. If the day one gets really wet and I have a cold start then I keep the night one on. (hoping to dry the other during the day or the next night)
I don't filter or purify unless the water looks "dodgy" to me (not a good system but that is what I do...) however I have Micropur tablets with me.
Here during summer/dry season I also carry a Pur Hiker pump because often the only water available is from ponds on otherwise dry river beds or some waterholes.
On longer walks I have my standard head lamp (or mini torch) and a Petzel E Lite (1 oz) .
Oh, yes , over 2 days I have a spare pair of underpants ( Ex Officio now, they dry very fast, even wearing them...)
Franco