Growing up during WW2 and joining in the scrap drive with my wagon turned me into a real scavenger/packrat. I collected scrap rubber and metal on the farm and my mother would take the collection into Denver when we had a need to go there.
When we moved to Boulder I went around the block and collected cans, newspapers, old pots and pans, and string and nylon hosiery. By the time I was 6 years old I was collecting every bit of hardware and nail I could. After the war my dad went to the munitions depot not far from our place in Oregon where we had moved and bought a keg of used and somewhat rusted nails. My job was to straighten them out and make the nails usable. After school I would spend some time at that task. To this day I can spot a nail or screw on the ground or on a street and ascertain whether it is usable or just FOD (Forign Object Damage) an air force term I picked up when in the USAF.
One time I bought a container with several hundred "O" rings in it from a Harbor freight Tools place and had no real use for them. one day a neighbor was fixing somehing and needed a rubber gasket for something and the "O" rings were brought out and it saved the day. I also had to have the cotter ring collection and have used one our two but they also were valuable at the time.
COSTCO had been selling the cran/raspberry juice in one gallon plastic containers with a neat folding handle on each one. They were great to carry when full and would make a decent water container. Now they have dropped the handle idea though. The one gallon apple juice containers are also good and make a great water container when travelling for car use. Your car may not overheat but there is always some poor guy standing around watching the steam boil up out from under the hood. Just leave him a gallon of water and go on your way.
The rolls of bubble wrap that are one foot by 240 inches long are great for packaging things for shipping and have other purposes as well. We were having a problem with cold air coming through the single pane windows of our small house. It made it uncomfortable to sit on the sofa with the vertical blinds open. We put up two pieces of bubble wrap, each approx 10 feet wide and one foot high and the cold air is no more problem. I will have to see if that keeps out heat in summer.
The plastic 20 pound containers that kitty litter Come in could be used for water for vehicles and other purposes. They could also hold regular sand to be carried in the trunk or back of a van for traction in winter and to pour under tires on ice patches when needed. I got stuck in Wyoming in my dads VW bug in 1959 when I drifted onto the shoulder and the flat pan under the car was resting on snow. I used my Levi jacket under the wheem for traction and after two tries was out of the snow. The slight abrasion on the jacket just made it look more rustic.
Some years ago I picked up two steel mess hall trays like I used in the army and have used them for parts trays and sorting trays for various projects. When disassembling a firearm they are good to keep small parts in.
Keep a couple of battery testers around for testing all batteries before installing them and when checking an ailing flashlight or radio. Twice in the past year I have come across a "new" battery that was DOA out of the package. Sometimes aradio that uses batteries on two different levels or rows will have one or two that fail or get weak first. By having a tester nearby you will save yourself frustration when checking them out. I have one in the bedroom, living room and my electronic BOB.
Now I need to get back in the garage and go through some more boxes!