After trying a few, I noticed the Kutsuwa Stad T'Gaal sharpener on Jetpens. Besides, the difficult name, it sported a unique dial on the front that caught my interest. The benefit of this sharpener is that you can choose between 5 different sharpened lead core lengths. In other words, this sharpener can give you a short, stubby writing length, a long, pointy writing end, and three degrees in between. There are a number of reasons you might want different core lengths, but most of them boil down to preference. For me, it was mostly curiosity because I didn't really know what kind of length I preferred.
For less than $7, you can buy a sharpener that gives you an idea of what different core lengths do to a pencil. In a way, each length setting gives the pencil a different character.
So, how does it work? Simple: just rotate the dial to the core length you want (represented by the numbers 1 - 5), and sharpen away.