related to pens & writing implements: make sure you have a pen on you in somewhere easy to get. admittedly my experience is mostly flying (so it's REALLY good to have a pen in your carry-on purse, not your carry-on bag and definitely not in your checked) for the invariable paperwork you find yourself filling out. Often midflight, because that's how Canada customs rolls.

IDK how long you're going but I also recommend some plastic bags for storing random things (that might get wet?), ziploc bags for small things, a purse you can store small stuff or a water bottle or what you normally carry in addition to what suitcase/backpack you're travelling with.

Also sunscreen.