It depends on what you mean "knife sharpening". Believe it or not this is a somewhat subjective term. How hard do you use your knives? Do they get completely blunt and need to be reprofiled back to an apex? And what type of steel is your collection comprised of? Very hard high alloy steels will require a different set of abrasives than basic simple steels at a lower hardness. How pretty do you want your edges to be? How much time can you spend sharpening? Do you want to relax for an hour long sharpening session, or do you want to sharpen all twelve of your hunting buddies' knives in the space of a few short hours?
For quick maintenance of dull, but apexed edges in most steels, the Spyderco Sharpmaker is fantastic. If you use it often, be prepared to wash the stones with soap and water fairly frequently to keep them cutting optimally.
For maintenance of apexed edges, and convex reprofiling of dull knives, the WorkSharp and Blade Grinding Attachment has worked fairly well for me.
If you intend to dramatically change the edge profiles on a lot of knives, get a belt grinder. You can very quickly set bevels $200-$300 with a 2 x 42 grinder and some 120 and 220 grit ceramic belts. Of course you'll have to pay attention not to overheat the steel by pressing too hard or moving it too slowly across the belt. And once you set your bevels, you can clean them up on stones, or on the WorkSharp.
These are just some ideas, and the answers to the question will vary as much as the number of people who offer them.
I typically grind a knife fairly thin behind the edge using my Dayton 2 x 42 for good cutting geometry, then give it a 15° per side edge on diamond plates (320, 600, 1000 grit, usually) attached to my Spyderco rods on the SharpMaker, then micro to 20° on the SharpMaker rods themselves.