Years ago, I bought a garnishing tool kit that included a small knife designed for making wavy cuts in vegetables. It was annoying to use and eventually it disappeared from my kitchen. I didn't think about making wavy-cut vegetables again until I got a mandoline with that blade.
Which is fine if I'm making a large quantity of bread and butter pickles, or I'm making salad for a crowd. Otherwise, I just use a knife and make straight cuts.
Kuhn Rikon's Krinkle Knife ($14) might just change that. It has the same wavy blade as the garnishing gadget from long ago, but it's in a mezzaluna-style knife.
The rocking motion of the mezzaluna makes cutting easier, particularly with harder vegetables like carrots, than trying to push a knife straight down. This also makes the pattern slightly curved rather than straight.
For less resistant vegetables like zucchini or cucumbers, you can easily make your cuts straight down, if you prefer.
The knife is thin and it comes with a plastic guard for the blade, so you can store it safely and easily in a drawer. But although it's thin, the handle is substantial enough to feel comfortable in use.
While a mandoline is probably the better choice for large quantities of vegetables, this standalone knife makes more sense for small jobs, like making salad or crudites for two.
It can also handle tasks that the mandoline can't, like cutting really thick slices, or cutting vegetables in halves, quarters, or chunks, like potatoes for a potato salad. Or even for cutting hard-boiled eggs for deviled eggs.
Making wavy cuts in vegetables isn't an essential task by any means, but with this knife it's no more difficult than making straight cuts. And it makes presentation more fun.
The knife is dishwasher safe, but I always suggest washing knives by hand.
Disclaimer: Testing samples were provided to Serious Eats.