Stones.
I'm a biased old fart, I admit that, but I don't like sharpening gizmos of any kind. I see them as an answer in search of a question. I may even see them as a snake oil solution to the problem of getting your money out of your pocket and into the manufacturer's pocket.
I think a very great deal of the problem is that, a lot of people never had someone sit down with them and show them exactly how easy it is to sharpen a knife. There's no rocket science here, just a blade and an abrasive surface. That surface can be a stone, diamond hone, brick, coffee cup, or whatever. Exact angle does not even matter, as the material being cut won't know if its 22 degrees or 26 degrees, while it's sopossed to be 25 degrees.
For the past 20 years or so, I've used diamond hones by Eze-lap and DMT. Both have worked well, and I can't tell a difference in effectiveness. Once the knife shaves hair smoothly, it's a moot point. Most of the time I only use the Eze-lap model L that I cut most of the handle off and keep in the zipper compartment of my wallet. I strop on the back of my belt.
Any good flat surface will do. Too many people over complicate and over think the sharpening thing. All you need is a flat diamond hone or stone, a dry erase marker, and a knife that needs sharpening. Never use oil. It makes a mess, and is not needed.
I'll tell ya what; If anyone here that's anywhere in the Washinton D.C./Baltimore/Martinsberg W.Va. area has a video camera, I'm willing to make a video for the traditional forum on how to sharpen your knife anywhere, anytime, with just one or two items you have on you. Just for my traditonal forum buds. I'll even cover coffee cups for ya.