The Ninja Foodi NeverDull System Premium German Stainless Steel Chef Knife and Knife Sharpener is wonderful!  The system is supposed to keep the knife razor sharp for over 10 years.  It has a foolproof stone sharpening wheel that delivers razor sharpness with just a few swipes of the lever.  It has a comfortable grip, but professional durability and sharp precision.  You slide the lever up and down 10 times for a sharpened knife.