QOTW: What ordinary household objects or everyday inventions are more awesome than most people realize?

Following on from last weekend’s question, about unnecessary human inventions, let’s talk about the flip side:

What ordinary household objects or everyday inventions are more awesome than most people realize?

Mine are Ziploc bags... all sizes are great, but the best are the freezer bags, because they’re heavier and more durable, in the gallon size, which is the most versatile and useful size. I use them for everything, from keeping stuff fresh in the kitchen to organizing computer cables to traveling with toiletries (spills stay contained in the bag and don’t mess up my clothes) and much more. In fact, I’d venture to guess that Ziploc freezer gallon bags are much more essential to the galactic hitchhiker than a towel.