For me it varies depending on whether we drive or fly, which is always hand luggage only.
I've stayed in too many places that don't have basic supplies in the kitchen, so if we drive I bring a few essentials like cooking oil, herbs and spices, etc. - the sort of thing you only need a bit of and don't want to buy. If we're flying I limit it to salt and pepper. But really, it would be nice to know this stuff would be there. The worst one was in Greece, we arrived about 10pm to find there was NOTHING to eat or drink in the kitchen, not even instant coffee. They also had no tourist information whatever in the flat, but many copies of leaflets promoting the owner's business
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We don't drink milk. One of the best welcome pack things we had was Ryvita thins, and new discovery for us and now a staple. Wine or cake is nice, but of course not everyone would want it.
We mostly cook rather than eat out, so things that enable a range of meals are good - an oven-proof dish, lemon squeezer, grater, sharp knives, oven gloves, decent-sized spoons for serving, garlic press, etc. I also prefer to have some serving dishes rather than having to dish up straight from saucepans.
More than one loo roll per bathroom - I don't mind buying loo roll if we're staying a few days, but having just one feels stingy.
Enough seats. On our most recent trip I nearly booked somewhere for 3 people with only 2 dining chairs; the next one on my list had enough dining chairs but just one 2-seater sofa. It gets tiresome peering at all the pictures in listings to make sure that the basics are provided - if it sleeps 4 there should be at least 4 dining chairs and 4 soft seats.