Necessity:
I think probably first the little vegetable steamer insert we have that fits inside pots and pans. I use that thing every day. Then the French press, without which I would have nothing to brew my Russian Smoky Tea.
Convenience:
Microwave. Don’t use it much, but when I need it (like last night, when I wanted steak and potatoes but had only half an hour to cook it – pop those taters in the 'wave, and no problem), I really need it.
Coolness:
Darth Mixer. Hands down. It’s the six-quart KitchenAid stand mixer, in “Imperial Black.” It dominates the countertop. It frightens small children. It makes cookies, meringues, and even soap, without batting an eye. It is the God of the Kitchen.
Other:
I like the miniature cheese grater, because it’s good for grating stuff into small bowls. I also love the nutmeg grinder. Not useful too often, but when you need it, it’s awfully handy. I would kill for an electric juicer. Yet another of those things that you don’t need too often, but when you do… I made homemade lemonade once, and let me tell you, squeezing out ten lemons by hand truly sucks.