I have one of those Grundig hand-crank shorwave radios with a light built-in. That is as far as I am prepared to go for a hand-powered light. That little unit will run for many minutes (best guess is 15-20) with both the radio and the light going after cranking it for one minute.

I also have a shake-light that is relegated to a kid's toy, in spite of being one of the $25 "Hummer" branded ones. It is too gimmicky. It might be useful if you were being banished to an island for 20 years with no batteries available. However, for any sort of real emergency, I think that I would rather have a Gerber Infinity. Heck, even a $6.00 Dorcy AAA LED light from Wally-World would be better. And I bet that you could pack one of those lights and a half-dozen batteries in a smaller space that a full-sized shake-light, and get more (and more consistent) light in the process.

With that being said, I have seen those lights for $3 at a flea market. For that price, you might want to pick one up just to satisfy your curiosity (and because you can never have too many lights). But don't let owning one stop you from buying something better.