I've got a Nightstar II shakelight and it's pretty nice. It has a reflector and crap to send most of the light out the front, actually does charge a capacitor by shaking (there's a novel thing for a shakelight to do, lol). Unlike alot of the cheaper lights it also have repelling magnets at the ends of the tube, so as you shake it the large magnet does not bang against rubber bumpers or anything at the ends of it's travel. It's pretty cool IMO. I got it to keep in my car so I never have to worry about batteries, I really like it for that.
They aren't as bright and don't throw the beam anywhere near as far as a regular light, but if you're like me and hate buying batteries and such they're nice. Make a great emergency light to keep on your bedstand or whatever to. I suspect some of the quality made cranking lights w/ mutliple LEDs may be even better.
Target carries the Nightstar lights BTW, they have the full size one that I purchased and also the CS model I think it is that is more compact. Fairly pricey too though really, but if you've already got a nice flashlight this one can fill a different niche IMO.
*Edit - Forgot the mention the thing runs for quite awhile without reshaking too. When it dims enough to notice a quick couple shakes and it's back to full brightness. I'm very happy w/ the Nightstar II...