Obviously fabric... and my favorite ruler, which is no longer being made and that is making me really sad. It was made by Judy Martin and when she discontinued it, I emailed her pronto and asked to buy any remaining rulers she had in stock. She said she had some used ones which she would discount. Sold! I bought every one she had left. It is the perfect size: 7 by 19 inches, which is the main reason I like it so much, plus it has clear easy-to-read markings every 1/8 inch, with none of those distracting yellow markings like some of my other rulers (I won't name names, but you know who you are). I use Judy's ruler almost exclusively and all the markings are wearing off (insert sad face here). I should probably accept the inevitable and start shopping for a new brand.
Thread: nothing better than Superior brand. It really is superior. Nearly lint-less. And you want to know about thread? Start reading Superior Thread's monthly newsletter. Who knew there was so much to learn about thread? At the risk of you thinking I need to get a life, I find all that information about thread pretty interesting.
Probably my current favorite tool, which I use for inspiration, is my computer, where I read all my favorite quilting blogs. Yeah, still trying to find a way to actually get paid for spending all that time.
So, thanks, Heather, for a great idea. March on...