I've mentioned before how much I like the Chef's Choice Trizor XV knife sharpener. It can convert a blade to the preferred 15-degree angle and then keep it good and sharp with just a few swipes. (Here's a demonstration of mine.)
But the price was a big turnoff for a lot of people.
Right now you can snag one at a great bargain: $105, down from the regular $150. I don't know how long this will last so don't wait. Get one for yourself or for your favorite cook. Remember: a dull knife is more dangerous than a sharp one.
Note: I never endorse items I do not use or would not recommend. If a purchase is made through one of these links, I may receive a commission.