Edgemaker

They make knife-sharpeners for kitchen and sport knives. Most people will use them on kitchen knives, so I put them under the Kitchen category when I submitted this business to Yelp.

I have the set of sharpeners called the "4-STEP SHARPENING SYSTEM - Restore, Sharpen, Hone, Polish". They are plastic handles with crossed metal rods to get the perfect angle. They say they can do serrated knives, but so far I've used them only on straight edges. Be sure to read the instructions or watch the online video.

Very little effort is required to sharpen a dull knife. They are ALMOST idiot proof (you DO have to read the instructions). No gritty mess that you get with dry stone or wet stone sharpeners. No guessing about the edge angle, it does it for you, you just "aim" for the center of the crossed rods, there's even an "aim spot" on the plastic handle. You do have to pull the knife through at the right vertical angle, 45 degrees for straight edges, 90 degrees for serrated.

These even restored some cheapy 25 cent so-called "steak knives" from China that I bought at a dollar store.

These did wonders on some $60 fancy carving knives, bringing them back to razor sharpness.

Also, keep your sharp knives in a knife block or rack or sleeve/sheath, don't let them bang around in a drawer, because each tap or bump of metal against metal dulls the blades a little bit. Also, don't wash sharp knives in the dishwasher where they will bump into other utensils, for the same reason. Dishwashing powder is also a mild abrasive, so it's best to wash your sharp knives by hand. Heat and soap in a dishwasher also prematurely ages wood handles, and removes any finish.

You can also see rave reviews on Amazon, search for "edgemaker".