With the kitties, it's the microwave. If JuneBug can't smell the wet food, she eats less so I put hot water in it (and electric kettles work SO slowly here in the US)

Without the kitties, my Caphalon hard-anodized nonstick skillet. It's the most used item and it's versatile to cook about anything in. I do need a new one, though, as it's getting a bit scratched