I was recently watching a PBS cooking show where they discussed essential items for your kitchen crock. Among the items listed was a stainless steel ruler. I'm not sure why this hadn't occurred to me before; I'm constantly trying to estimate the size of rolled-out dough by holding my recipe printout up to it (with greasy/floury hands, of course), or digging through my sewing cabinet when I can't remember if my springform pan is a nine- or ten-inch model. It would also be good for cutting perfect strips for a lattice crust or a grid for homemade crackers.
One use I would never have thought of was for reducing liquids. To reduce a sauce to a particular amount called for (say, ½ cup), measure the depth of that much water in the pan you will be using in advance. You'll save yourself a lot of pouring scalding-hot liquid back and forth.
The trick seems to be finding a ruler without a cork backing. If you're searching online, look for double-sided rulers, such as this model, since they're sure to be steel-only.
So, what else am I missing out on? Do you have any unusual tools in your kitchen arsenal?