I used this sickle weeder:
I looked at this a long time before I got it. It looks kind of scary but it really isn't. If you have the sense to use a kitchen knife without opening an artery you can use this -- just keep your fingers out of the way!
And it's fast, too -- by the time you persuade someone to do the edging, they get gas for the weed trimmer, they get back, do the edging and put the trimmer away, you can be done with it. And it doesn't use up any power.
It's not only great for edging, it's useful for cutting high grass, stands up fine to working around concrete (although that does dull the edge after a while but that's what sharpening files are for) and can cut pencil-sized saplings that try to take over (somewhere around here we have an elm tree that is doing just that). Just hold on to the top and whack them at the base.
Someone left a review there at Amazon that it seemed small for him. I have a large hand for a woman (medical people, I wear a 7 1/2 glove) and it seemed just fine for me. So unless you have a really huge paw you shouldn't have too much trouble with it. But it is NOT for lefties -- there's no way to reverse the blade that I can see.
So there you go! I love it, and use it all the time.