I recommend the 3-stage Chef's Choice sharpener. It is an expensive diamond-based (only industrial grade diamonds of course) electric unit of very high quality. It provides different slots and different procedures depending on how dull the knife is. I had a drawer full of ineffective sharpeners before I bought this one which has given excellent results for many years. I believe that I paid about $70+ for it. Be sure to follow the very clear instructions, and do not attempt to sharpen serrated edges or scissors with it.

I also recommend buying a high quality fillet knife from a butchers' supply store. An old-fashioned carbon steel knife can be relatively inexpensive and take a very sharp edge. I have had mine for many years.

The best low-tech sharpener I used before the Chef's Choice was a two-sided rectangular honing stone (coarse and smooth sides).

Good luck.