1. Bathing suit
Swimsuit shopping on the fly is a) not fun and b) a waste of money. Keep an old one in your suitcase so you're never without. Your plans at the outset of a trip might not include a pool, but things come up. You could decide to visit a spa, realize you do need some time in the hotel hot tub after a day of walking, or meet a wealthy stranger who invites you to stay an extra day or two on his or her yacht. Hey, it happens.
2. Corrective lenses
If your vision is far from 20/20, pack backup gear: extra contacts or an old pair of glasses that could work in a pinch. Things get lost and broken, and having to visit an optometrist on the run is, at best, a costly, time-consuming problem and, at worst, impossible. After forking out thousands of dollars for, say, a cruise to Antarctica, the last thing you want is to not be able to see the penguins.
Tags on new clothes, loose threads in old clothes, broken nails, hangnails – you'd be surprised how often the need to cut something comes up on a trip. You can pack scissors in your carry-on (blades six centimetres or less, measured from the fulcrum to the tip, are permitted, according to the Canadian Air Transport Security Authority), but in a pinch even a pair of nail clippers can handle small jobs.
4. Document copies
It can't hurt to keep a photocopy of your passport in a bag separate from the original, but uploading one to the cloud will do just fine in most cases. The key is that you're able to access it easily if needed. Consider storing digital duplicates of your credit-card numbers, health-insurance card and driver's licence. If you don't trust the Internet, leave the info with a trusted friend back home.
5. Shampoo and conditioner
Yes, most hotels provide these basics. But 95 per cent of the time they are truly terrible. Combine them with one of those hair dryers that is attached to the wall and you're guaranteed a bad hair day. If you have even an ounce of vanity, do yourself a favour and at least pack a decent conditioner.