Duck tour? Well, it involves quacking. No, seriously. In addition, it's one of the most highly rated tours of Boston, both for fun, as well as for historical accuracy. The cool thing is that they are done in old WWII amphibious vehicles, so you start out the tour on the streets of Boston, and ends up driving into the Charles river.
And you do quack. The tour guides are fun, and when you pass large groups of tourists (or Boston residents...), some guides will have the tour group quack loudly at them. (To the point that there is at least one neighborhood that passed a "no quacking" ordinance; on our tour, we all just quack whispered.)
Here's a
link to the duck tours. Have only done it once, but it was fun!