Ask any parent and they'll tell you the best toys are the ones that leave kids exhausted and ready for a long peaceful nap. So instead of buying them a traditional RC toy car that chews through batteries or leaves them bored while they're waiting for it to charge, consider the $20 DynamoGo which makes them earn every last second of playtime.
The tiny RC cars are charged by the wireless remote which includes a folding handle that requires kids to crank for several minutes before they can play. The length of playtime is far outweighed by how much cranking is required, but that's good since it teaches kids that hard work comes before play, or it builds character, or however you want to disguise the fact that you're just trying to tire them out so they go to bed early. Kids are gullible, you'll think of something. [ThinkGeek]