In my career, I found the best team building took place in a very well planned and orchestrated team meeting. They weren't common and participated in lots of time-wasting recurring team meetings - but that wasn't the case with those that were well planned, had a specific goal, expected everyone to contribute, valued ideas, and recognized them appropriately.  I've been involved in a wide variety of team building exercises, but I still vote for the nothing special except that the exchanges of information and strategies proved to be significant.