I like this one, from Radio Flyer. It is classic looking, and doesn't have activities, but holds fun toys, stuffed animals, etc... so it doubles as storage. It has a special locking mechanism so the wagon doesn't roll away from the kiddo if they fall down... something about when there is downward pressure on the handle from the child running too fast or falling forward, the wagon stops rolling easily? I can't remember exactly how it works, but it was definitely a favorite and seemed to work very well when my kids were learning how to walk. They still play with it at 4 & 2. The only trouble was they'd walk as far as they possibly could, hit a wall and then yell until someone would come and help them turn around to go again.
http://www.amazon.com/Radio-Flyer-Classic-Walker-Wagon/dp...