I think every person who has a hobby has a favorite tool. Mine is kind of lame to many people and I didn't grow to love it until I started doing projects with more counting involved. My stitch counter is simple, inexpensive, and makes my crafting a breeze. With two small children running rampant through my home, there is no way I could keep track of where I am in a pattern without my stitch counter.
What is your favorite tool?