As a frequent traveler, whether local or international, I always have a weekend bag packed and know what goes into my international bags, work and vacation – though I’m not sure when I last had one of those. Needless to say my camera bag is always at the ready, like sports gear, when you come home, you reset, so I will skip that one.
I don’t believe in buying things on the road when you have the items at home, so here are some critical things from years of experience. And in many countries you cannot get things you might consider essential or as on Sundays in Zurich when you have a bad cold, you cannot find goods so best to always be prepared. Of course shop local if you can, but I have some links as well if you cannot.