I'm disabled so some of this is my own adapter items
Can/bottle opener
Tea towels
Sharp knives
Mugs (I need light ones with decent full hand handles)
Foil (I can't get on with cling film and use foil when many others would use cling film, it's also very handy for creating "lids" for oven dishes)
Oven gloves
Own loo roll - TOO MANY times of getting thrush/allergy reaction to coloured/perfumed loo roll that accommodation organisers have bought to impress! I'm best off with the cheapy stuff PLUS it flushes better!
Extension cord of the type that means you can plug in severely items to one outlet
Also usb multi adapter as recommended on here
If staying outside of Scotland I'll take scottish tea bags with me.
In my first shop there:
Kitchen roll
Food bags
Cooking oil
Laundry detergent (allergies)
Admittedly I have ocd but also scourers, cleaning spray etc Usually end up buying fairy too as I really can't be doing with cheap, crap imitations!
Matches
As well as food of course
Slow cooker is an excellent idea.