How is a rice dispenser useful? I have seen them and wondered why they are better than just pouring rice out of the bag. I’d get one if I knew why they are good.
A completely unnecessary but wonderful gadget is the Panini Maker, guarantees perfect delicious toasted sandwiches, mmmm.
The most essential gadget in our kitchen is Mr. Athena’s Homer Simpson bottle opener. “How 'bout a beer? glug-glug-glug YES OH YES WHOOHOO!”
That, and our champagne stopper. Both must-haves.
If you are part of a large Asian family that eats rice at practically every meal, you buy rice in 50 lb. sacks and keep it in the dispenser.
Pressure cooker. Brown rice in 45 minutes? But I want it to be done when my stirfry is finished! Tender beef is expensive? But I want to pay $2.95 a pound and have it fall apart under my fork!
Ceramic ginger grater. I cook a lot of Indian and Asian food, so I go through a lot of fresh ginger. It’s too stringy to use a normal metal grater. My microplane grater just can’t get a hold of it. (It’s an extra-fine; maybe a coarser microplane grater would be better.)
Mandoline. Thin, uniform slices, ridiculously fast. But always always always always ALWAYS use the hand guard. Don’t just think, O, this potato is large, I can hold it by hand for the first few slices. It’s too easy to misjudge. Wanna see my scar? It’s that quarter-inch oval there right on my fingertip that doesn’t have any fingerprint on it.
Salad spinner. I resisted getting one because it takes up so much space, but I finally broke down. Hey, clean, dry lettuce, much cheaper than the bagged, pre-washed stuff! It’s also useful for spinning out handwashing. Yay for multitaskers. And turns out I can store it with the lid underneath, and mixing bowls inside, so it’s not a spacehog.
Fat rubber band. Like the kind that comes around stalks of celery or broccoli. This is the best tool for opening stubborn jars. Just wrap the rubber band around the lid, and I guarantee, it will come off with a gentle twist. And you can’t beat the price.
My stick blender is not a gadget. With God as my witness, I will never puree hot soup in batches again. My spice grinder is not a gadget. Pre-ground spices suck.
And unlike plastic ones, they will actually come clean. About a year ago, we threw out our perpetually grungy, geasy-feeling, nicked-up plastic measuring spoons and cups and bought two sets each of metal ones. So much nicer. I’m on a plastic jihad in the kitchen. If it can be replaced with metal or glass, or I can do without it, it’s gone. Plastic mixing bowls, I am looking in your direction.
I had never heard of a mezzaluna before opening this thread. Now I need one. Badly.
I have a mezzula oblongata 
I make my pie crusts in the KitchenAid using this method. So the KitchenAid would be my first gadget of choice (above those I mentioned above), but they are rather pricey for the powerful ones. If we are talking inexpensive, then I agree completely on the pastry knife.
–The Microplane grater with slider attachment. Perfect for hard cheese, garlic (when I want it finer than I’m willing to mince it by hand), and nutmeg.
–The digital thermometer with alarm.
–The kitchen scale. My baking went up a level when I finally broke down and invested in a decent one.
–The stick blender.
garlic [del]condom[/del] sleeve, for peeling garlic
That’s a good one that needs repeated. Measuring by weight instead of volume leads to much more consistent results when baking. 270 g of flour is much more precise than 2 cups.
Microplance grater.
Electric fryer
Oil / Candy thermometer (I don’t fully trust the settings on the
Meat thermometer that beeps when temperature reached
Pasta pot
Pressure cooker (is this really a gadget - I consider it a necessity!)
Garlic press
got one. love it. 
ditto
must try this at next opportunity ! thanks !