If I had to pick a sharpener for an extended trip, I am not sure what I would pick. I have used many of the above, but usually at home. Fishing I have often used one of the small Eze-Lap rods, and that would be my first choice for durability, light weight, and emergency use, if I had to quickly choose one, and did not want to rely on the one on my multi-tool.
Other alternatives that I have not seen mentioned above are:
1. a. Diamond coated wet & dry "sandpaper," for wallet or other carry. I read on BladeForums that it exists, but have never seen any and have no source. Anyone have any information?
b. other abrasive papers/cloths. Any favorites?
2. Gerber also makes a round/flat/groove rod which is aggresive, but I do not know the grit. It has a lightweight aluminum handle.
3. a. Wallet or credit card sharpeners. I understand Eze-lap is making these. Apparently there is a combo model too. One person wanted to glue some abrasive paper/cloth to one of his plastic cards. Anyone have any comments? I kind of shiver, thinking of sliding one of these down the long, sharp, edge of a Battle Mistress....or Nordooh, etc. I guess you could place it on something and pull the knife down it, or otherwise just be careful. It would be convenient to fit it in a wallet, as if I had any more room there. Hardly any money and still too thick.
Might set off metal detectors.
b. If nothing else it would make a dandy portable fingernail file, like the Leatherman Wave diamond file. Anybody ever try the diamond fingernail files for knives?
4. Gatco triceps. Just managed to get one of these and like it. It worked OK free hand on a knife. The selling point are the built in angles, but I have not measured or used those. Anyone know what they are supposed to be? It is triangular and about the grit of a coarse Spyderco sharpmaker. It has various edges and grooves. After I twisted Brian's arm at Discount Knives he ordered some, in addition to the ones I got. It is supposed to be durable, and I read a magazine article that suggested it had been tested by some military outfit. Might be OK, since even if broke you would still have a piece, or find a rock, etc., ...I doubt if one's survival would be impaired.
5. Aready mentioned by Ron, an improvised strop would be convenient. I had the same idea, but Ron has practiced it and crystalized the idea, by suggesting an effective method. I just got a hone from
http://www.handamerican.com and the knives I have used on it got much sharper, so I like that idea. Hmmm...how about putting a little of the included honing compound on one of your tinder cotton balls. Use it to treat your favorite in-the-field strop and still have backup tinder.