This is not a very sexy post and there is probably nothing in here that a seasoned traveler does not know, but just in case...
Whether I am gone for a week or a month (I wish), I take no more than a carry-on suitcase (less than 6 pounds empty). However, I always pack two or three plastic plates, plastic forks and knives, zip-lock plastic bags, and a tire-bouchon (wine opener). None of these take up much suitcase real estate or add any weight.
As you look at the above photo you can see why. There are times when you started early, ran all day, and when the sun went down at 11pm (yes, in the summer it does!) you were simply too tired to sit in a café (make that another café). So, you grab une bouteille de vin, une bagette, des fromages and you can have a little respite in your hotel or your apartment. It is also handy when you are going to do macaron research -- more another time on that topic (miam-miam).
Regarding le tire-bouchon, I had the simple plastic "hotel-type" opener taken by security as I left Paris headed to the USA, but it had been to/from Paris 4 times, to South America twice, and many other places. So, I feel less certain about transporting than I did previously.