Generally, I am not a fan of unitaskers, those kitchen tools that have only one purpose. An asparagus steamer or a fish poacher may be just the tool for the job, and if storage space is never a problem, you may want one of each, but for a practical home kitchen, we just don't have enough room for every device that comes along.
That said, there is occasionally a tool that is just the one you need for a task, and no other tool seems to do as well. One unitasker that gets a place in my kitchen is an egg wedger -- sort of a tong like device that has a cradle on one arm to hold a hard-boiled egg, and on the other arm a criss-cross of wires that, when the device is squeezed together, slices the egg into six perfect wedges. Perfect for one of my specialties, Salade Niçoise!
What's so great about it? Well, for one thing the slices are uniform. I find it much harder to get nice even wedges using a knife. Quartering is a bit easier, but making six uniform pieces is more challenging.
Also, the pieces stay together. When using a knife, it isn't unusual for the yolk to stick on the knife and pull away from the white. With a little care using the wedger, the wedges remain intact, meaning no pieces of white uncurled from their yolk.
Finally, it's cleaner and faster. Little bits of yolk clinging to the knife stick to the next slice leaving a yellow rim. Fussy, I know, but easily solved with the wedger. You can avoid the mess by repeatedly dipping your knife in warm water, but then you take more time and end up with a water slick on things. With an egg wedger, one brief squeeze and you're done. Neat, clean, even pieces in nearly no time at all.
Sometimes the payback on a unitasker justifies its existence. This is one of those devices.