Wusthof Diamond Sharpener, Fine, Oval, 26 cm (10-inch) - 4483

Excellent value in a diamond sharpener. If you want a diamond sharpener, in my opinion this is the way to go. It's coated with industrial diamonds in a "fine" grade, so you can really get a nice edge without risk of damage from too agressive cutting with a "coarse" version, and the long length and oval shape means you get excellent control and consistency with maximum efficiency (the oval design helps with additional surface area). Note: this does not replace a traditional steel, which is more for maintaining and edge, whereas a diamond sharpener actually removes metal for restoring a dull edge that a steel isn't helping anymore.