Ok so the title is a personal opinion statement, but the recent file sharpening thread got me thinking.  I am a file sharpener also but as was stated its not good on knives, or at least none of my buck knives. So in my hunting gear I would always keep my file and my butchers hone and a little 4 inch medium arkasas stone for sharpening around the camp, and I like the lansky puck for my hatchet. But the Smiths 4"Diamond combination sharpener is by far the best all around sharpener I have EVER used.  I can use it like a file on my BH and use it normal for my knives, and i can also if needed push it along for my Hatchet also. I just love this little thing, and can get any knife or BH razor sharp in absolutly no time.  Here is a link to the video of it for those of you not familiar with this.  http://www.youtube.com/watch?v=R915rWqF8o8

This is a cool little shapener!  Where would one pick one of these up?

I just found it on Amazon for $15.49 plus shipping.

I have a couple of these as well and they are sweet, most hardware stores and places like bass pro/gander mtn carry them

I got mine at Walmart a few years ago for like 14 dollars

Word of warning if you have never used a diamond sharpener before , go really light in the beginning to learn it. It cuts faster than stones and files in my opinion.

UPDATE!!!!
So I am paired up with a new mechanic at work, and the other day while working on an elevator we needed to open up a box, so my partner pulls out a Buck Stockman, ( i love these knives) and goes to open the box. NADA, i have butter knives sharper than this. I don't think it was sharpened in 10 years.  So I take the knife home, and NO JOKE within 10 min I have all three blades hair shaving sharp with this sharpener.  Very Very affordable, and unbelievably effective.  I have one in the truck, one in the hunting pack and one in the kitchen.  Do you self a favor and pick one up.

Smith diamond sharpeners are my favorite. I have that one, but there is a small one I keep with me when I hunt for broadhead touch ups or knife sharpening. It is a little guy that folds like a butterfly knife and is maybe 3" surface, and is really light and small.

Over,
I have that one also.  It is very good.  It has a keychain on it I think. I have misplaced it somewhere, but I'm sure its not far.  

I bought my mom the oval fine grit stick sharpener. Its like 10" and  looks like a butchers steel (she is a chef, and its used daily at work)