I would put Swiss chocolate bar on the list for Switzerland because it is the kind of thing that feels useful once you are home, not just another airport purchase. Look for a boxed version with a decent date on it, especially if you are buying it near the start of the trip rather than at the airport. I would look for it in a proper local supermarket, covered market, deli, pharmacy, gift shop or small producer rather than leaving it until the departure gate. Back in the UK, it is worth checking specialist shops first because they often stock a better version than a broad marketplace listing. The reason it works is that it gives you a quick reminder of the trip without needing to keep a fragile ornament safe forever.