Some incredibly useful forehead-slappers I have learned from Mr. Alton Brown...
Heat-proof gloves for oven mitts: Go to the hardware store and look for welding gloves. They're leather, far more protective than kitchen-type oven mitts, and they have fingers, so you can wrangle hot, difficult things like an evolved primate.
#16 ice-cream scoop for muffins: In art, my medium is muffins. Scooping the batter into the muffin tins is always the most difficult step: time-consuming, likely to spill on the counter, wispy scraps of batter around the outsides of the tin burn and affect the flavor, and you need to do it fast so you don't lose all the fluff from your baking powder. Enter: ice-cream scoop. A #16 is the perfect volume, and the thumb trigger dumps the batter right on target.
Egg slicer, with blades, for mushrooms, strawberries, what-have-you: I used to think egg slicers were a unitasker, but I just wasn't thinking creatively enough. If you get one with metal blades instead of wimpy wires, you can quickly slice anything small and squishy. Which includes the tips of three fingers in one efficient pass, so watch yourself. *sniff*
Cast iron skillet: Somehow I took it into my head that cast iron is difficult to clean or care for or cook with. I don't know where I got these ideas, because they are completely wrong. My cast iron skillet is the most used thing in my kitchen. Okay, to clean and care for: Follow Lodge's instructions to season it once; from then on, clean only with water and a scrubbie, dry it right away, and coat it from time to time with a little fat (cooking spray, butter, or... bacon!). The easiest way to clean it is to dump water in it right after you take food out of it (deglazing, the foodies call this), scrape off the bits with your spatula, and dump the water out. The heat of the pan will probably dry it in a hurry, or you can wipe it with a towel if it has cooled. Then, as far as cooking goes: For nearly every application, the weight and heat inertia of a cast iron pan will make you so happy. With a wimpy aluminum pan, as soon as you add ingredients, you cool the pan way down. You'll never get a nice brown crust on a steak with an aluminum pan. And with teflon pans, you have to be so neurotic about which utensils you use and how you wield them. Mr. Cast Iron is not afraid of anything in my kitchen drawers.
I could watch Good Eats all day, and I have no self control when there are Alton Brown DVDs in the house. I like the nerdy food science, and I like his "Anyone can cook!" approach to cooking instruction, but my favorite parts are the world-altering revelations of new ways to use kitchen implements. "Holy cow, why didn't I think of that? This changes everything..."
Do you have any Ah Has?