Although it's by no means an essential addition to your food-cutting arsenal, this traditional French tool―made of metal, plastic, or both, with a variety of blades―can be an enormous time-, effort-, and wrist-saver. The mandoline's virtues are lightning-fast speed and versatility. With very little effort, you whiz food back and forth across the blade to make julienned (matchstick) carrots, superthin slices of salami, thicker ones of bell pepper, or waffle-sliced potatoes.
If you make a lot of apple pies or sliced-potato dishes, try using a mandoline instead of a knife and you may not believe you ever lived without it.
Because the blades are razor sharp, this tool must be used with care. The simplest and best ones (like the Oxo Good Grips version, shown here; $70, oxo.com) have extra safety features, such as rubber-tipped feet to prevent slippage and a sturdy food gripper to protect hands from the blade.