Excellent Post, although we are no longer forced to make some of the cost cutting decisions we made in our earlier years, here are some of the items we bring on EVERY trip we take. Some are for cost savings if needed, some for a comfort & convenience and some because they may be hard to find if needed.

Gatorade G2 Powder, just add a little to the water and stay hydrated or use to mix with your favorite adult beverage
Can or Bag of favorite nuts
Pkg of 8 snack crackers &/or box of Nature Valley bars
Couple of pre-packaged cereal bowls
Bug Spray
Sun Screen
Aleve or some kind of pain reliever
Claritin or decongestant - different pollen and blooms can play havoc on your sinuses and can ruin a day or 2
Liquid Band-Aid or super glue for cuts and scrapes which can get infected

These items will take up very little room in your luggage but can be invaluable and you can leave them behind for a local friend or hotel worker, they will be very pleased.