"Best" is a dynohub with a Lumotec IQ Plus paired with a taillight.
Nice bright light, long lasting, and doesn't run down batteries.
I don't have one, but another BF'er does, and I'm jealous. I like everything about my Dinottes except for getting caught at 5 AM forgetting to change the batteries (only necessary once a week or so, but each time I'm plugging in the charger I think, "I should get a dynohub...")