Giant rubber bands are useful for holding together stacks of paper, and attaching objects using the double-loop technique. I also use them as an emergency hair tie.
In moving, I have used giant rubber bands instead of Bungee cords when I use the hand truck. It holds the boxes pretty well. Another use is the sandbox lid on windy and stormy days. I have used them on a toy box and around those large dog food bags.
People tend to have a lot of loose junk around their houses and a giant rubber band would help hold it together. Also, if you make a rubber band ball, sometimes you need a giant one when it gets too big.
