1. The best is to learn with a stone(s). However, that takes time and patience and experience. Most people do not learn this until they use a different system which teaches them about sharpness and how to obtain it. Cheap.
2. EdgePro Pro. Expensive, but will take care of just about anything.
3. Spyderco Sharpmaker (204). low price, will handle absolutely everything EXCEPT reprofiling very thick edges, and sharpening less than 15 degrees per side (though the stones fit in the base for use as a flat stone).
The sharpmaker is fantastic for serrated blades and for putting a final edge on after reprofiling. It comes with detailed instructions and a video.
4. Sandpaper on a block or a mouse pad. Used like a stone, or stropped to get a convex edge. Cheap.
5. Lansky/Gatco - Great for reporfiling and if you get the ultra fine stones, will put a wicked edge on (so will all of the above). This is pretty foolproof, but it is lousy for long blades (you have to re-clamp along the length of the blade) and is troublesome for blades that aren't very wide. (Hard to clamp them in tight enough). About the same price as the sharpmaker.
There are others (razor's edge etc.. ), but these are the ones I am comfortable reccommending. I have not used the EdgePro, but the rave reviews here are convincing. I had a Lansky system that broke and I much prefer a combination of the sharpmaker and and sandpaper blocks/pads along with an extremely coarse diamond stone for major modifications.
Other very useful sharpening info here: FAQ #9:
http://www.edcknives.com/faqs.html