I left my debit card in my room of the hotel in Saigon, and didn't discover it until I was walking down the street in Hanoi. Lucky for me, I had stayed at an incredible place in Saigon (Bich Duyen Hotel) where the manager bent over backwards for his guests, and he expressed that card to me PDQ. That could have been a very short trip to Vietnam!
Depends how long you are travelling for but..... bull clips, uno cards (or playing cards) and a light weight knife, fork and spoon set.
Bull clips are great for doing up little bags of food such as cereal as it is expensive to throw food out between places if you are travelling for a while. Uno cards, well to kill time with people you meet (playing cards are good for drinking games but) and a knife/fork/spoon set for places such as Croatia where kitchens in hostels are not common.
But, I managed to buy all of these things while I was travelling.
i havent been on my travels yet,got a couple more months to wait,but this has been a very good read in terms of things i now might be taking!
Since most of the folks I met along the way are from Europe and Oz, they didn't know the US geography as well as someone who lives her (obv), so I wld recommend a small map of wherever ur from. Helps connect w people and give them a better sense of where ur from and about.
A head torch.
A small four plug power board so that you can charge your laptop, mobile phone and camera batteries all at the same time. I only had one plug adaptor so could only charge one item at a time. None of my stuff charges through USB connections.
You can never have enough plastic bags to put shoes, wet clothes and other stuff in. Supermarket size shopping bags are great for this.
If you're a woman, bring a moisturizer especially when you're going somewhere hot and dry. I once forgot about my camera (which is stupid, actually) so don't forget that. And sometimes, a good book. Sometimes you just need to sit down and relax with a good book.
I know it's supposed to be a truism that everybody overpacks for their first big trip, but I did the opposite. I needed everything that I brought -- with the exception of some of the emergency and first aid supplies, obviously, which you never really want to have to use -- and found that there were a number of things that I hadn't brought with me but really wished that I had.
Similar to the cheese slicer, I now always take a tiny cheese grater with me, ever since my first trip when I kept running into situations where I wished I had one. Some of my friends, who are acolytes of the Cult of Packing Light, laugh at me for this, but when I can grate some cheese to make a sandwich or to dump some protein into my instant mashed potato, I feel it's well worth the tiny amount of space it takes up in my pack. Outdoor shops sell very small light-weight ones that are designed for backcountry backpackers.
Probably the weirdest thing that I pack, and something that I've never seen on anyone else's packing list, is a tiny nail brush. I consider it particularly important if I'm going to be camping or traveling somewhere where sanitation standards aren't that great. I use it to really scrub my nail beds when I wash my hands. It works with hand sanitizer as well as with soap and water. Because of the way my nail beds are shaped, I can never seem to get my fingernails as short as other people can, so the nail brush helps me keep them clean. I give the nail brush a dunk in boiling water whenever I can to sterilize it. Again, people may laugh and make jokes about over-packing and OCD, but they're not laughing when they get the runs every time they go traveling. I never come down with traveler's diarrhoea unless I do something obviously ill-advised, like taking a gamble on a high-risk foodstuff. I could just be lucky, I guess, but I can't help but feel that my little nail brush might have something to do with it.
One thing that I've only recently started carrying with me is something that I've seen t_maia champion on these forums: a plastic tupperware-like container with a tight-fitting lid for my lunches. It's bulky, which is why I resisted carrying one with me for so long, but when I don't have one, I always wish that I did. I'm tired of squashed sandwiches, smashed hard-boiled eggs, and bruised fruit. I'm also tired of feeling compelled to eat the entirety of an enormous take-away meal in one sitting, because I have no way to store the left-overs for later. The tupperware container also does a good job of protecting the rest of your stuff from the smell of stinky foods, like that lovely hunk of local cheese you picked up at the farmer's market and which should last you a number of days, if only you can stand to carry it around with you that long. The lid can also double as a cutting board (if you're careful not to cut right through it), and in a pinch, the container can double as a little sink. I keep a spork inside of mine and put a stout rubber band around the outside, just to make double-sure that the lid stays on.
On that subject, stout rubber bands (or elastic bands, or whatever you call them) are something I didn't bring with me on my first trip and kept wishing that I had. They take up virtually no space and are very useful to have on hand.
A couple of paper clips are also useful to take along. In addition to their usual purpose of holding papers together, you can also rebend them to use them as wire to hold broken zippers shut and make other such temporary repairs.
Extra buckles that match the most important buckles on your backpack. Outdoor shops sell them individually - you can bring your pack in with you and match them up in the store. You don't need the entire complement of buckles and straps (for many of them, a bit of cord will do the trick just fine), just the most important ones. At the very least, bring a spare for your hip belt buckle. Again, it takes up very little space, but should your hip belt buckle somehow get broken (as mine did when I accidentally trod on it at just the wrong angle against some rocks), you'll appreciate having a spare. It can be hard to track one down unless you happen to be in a trekking-oriented area, and your pack's suspension system really depends on it.
Not an item, but a bit of knowledge: if you have a strong preference in common over-the-counter remedies, take the time to learn what they are called where you will be traveling. You can pick the same stuff up in many parts of the world, but it may be called something different there. If ibuprofen is what really does the trick for your menstrual cramps or your trick knee, for example, then it can be quite frustrating to have no earthly idea which of the assortment of boxes of pain reliever you see for sale in the shop actually contain it. Bear in mind that even "generic" names for drugs are not truly universal; there are differences in generic names for drugs even between countries that ostensibly speak the same language! Asking for generic 'acetaminophen' will do you little good if you're in one of the many English-speaking countries where that drug's generic name is instead 'paracetamol.'
The thing that I always forget to pack, for some weird reason -- and then always deeply regret forgetting -- is a towel. You'd think that thanks to Douglas Adams, no one would ever forget their towel, but I seem to have a blind spot about it. Drying oneself off with shirts and such just doesn't cut it, especially in a humid climate where they'll then take forever to dry. I favor those viscose pack towels sold in outdoor shops. Their texture takes some getting used to, but they're light to carry, dry quickly, and don't get mildew.