This week's poll "winner" could very easily go to the "Other" category, because you may have highly specific things in your house that you couldn't homeschool without.
I know that when my boys were in the first couple of years of homeschooling, our most indispensable homeschooling tool was a set of brightly colored "fidgets". What in the heck is a FIDGET, you ask?? Fidgets are little devices, often soft and rubbery, but can actually be any shape or texture, that you use to keep your hands busy. The only possible way I could get my younger son to sit still enough to finish a math lesson was if he had at least one hand busily manipulating the fidget of his choice. Those fidgets effectively corralled his attention and gave him focus when nothing else would.
Today, without a doubt, our homeschooling would be essentially impossible without a computer. But I'm looking forward to finding out what device, tool, or resource your homeschool wouldn't be complete without!
p.s...I didn't include books, pens, or paper on the poll because I'm assuming it's a given that you couldn't homeschool without any of those!