There are many good knife sharpeners on the market today. The main factor in sharpening a knife is the device you use to remove the material from the blade must maintain a uniform angle for you and not allow your efforts from stroke to stroke to change the angle of pressure you are putting on the cutting surface of the blade. If this angle of relationship is changing from stroke to stroke, you will end up with a rounded edge that will feel sharp for a short period of time and dull rapidly.
A wide variety of sharpening tools including an extensive selection of Arkansas stones and Norton India stones as well as Diamond Whetstones. There are also a variety of ceramic and diamond rod systems.