So I have to honest. Before I met my husband, I had no idea what a Microplane Grater/Zester was - yet alone how to use it. And now, I just can't cook without it! I use to it to zest citrus and grate Parmesan. The best part is that when you zest or grate - the raised edges of the microplaner keeps all your newly grated deliciousness in one place so it's easy to carry to the pot or bowl. I have also used to "mince" garlic. I know it's not properly mince - but it is really hard to cut up that tiny clove of garlic into super tiny pieces so I cheat with the microplane as my accomplice.
What about you? What's your kitchen gadget that you just can't cook without?