10. Collapsible Water Bottles
The TSA will not let you through the security checkpoint with any open containers of water, but they will not stop you from putting empty collapsible water bottles into your carry-on.
This will become very beneficial if you end up stranded somewhere without easily accessible water.
After all, you can fill up each of your collapsible bottles when you do find a water source, and this will give you the ability to carry this life-giving liquid with you while you look for help.
Collapsible water bottles are also perfect in any other SHTF situation because you will always need the easiest possible way to keep water on hand at all times.