In my opinion, the two best projects were the "Grow School Greens" and "Underground Railroad". I think these make good use of the time it would take to accomplish them, they incorporate many school subjects into one project, and they give the students a chance to collaborate and learn to work in groups.
I think the two worst projects were "Where is My Hero?" and "Ice Cream". As I mentioned in the worksheet above, the Hero project would require a lot of the work to be done at home. The Ice Cream project would be messy, and it only incorporates one school subject.
To me, "best" means the most efficient. I appreciate projects that made good use of the time spent on them, and also incorporate as many subjects as possible. "Worst" would be the opposite--too long without actually teaching anything, and only incorporating one content area.