I have the map of the city (always have that anyway).
Water and some snacks in the car (if DD hasn't raided it too badly).
In boot, a box with
WD40, work gloves, decent bright flashlight
Re-usable handwarmers (click to heat type)
First aid kit (small - few wipes, few bandaids, 1 elastic bandage, 2 pairs gloves)
I also have a USB connection for the cigarette lighter, and a cable for my phone - but I need an older connection as well for DD's phone.
Tissues, hand wash gel, bag of change for car parking/emergency chocolate etc.
Once winter really sets in, I always have spare hats and gloves in the boot, and aim to have a spare blanket there too (loads of fleece ones at home). (There's normally a lifejacket, and often waterproof boots and trousers, there as well - in winter, I have proper outer gear and a spare layer there if the weather is going to be bad). I also have enough hi viz indoors, that I should really throw 1 jacket into the car.
I keep meaning to get some cat litter and a shovel. And jump leads. The spare tyre and jack are all working (I've checked), the emergency kit is there (triangle etc) and I have a battery charging yoke for emergencies also.