Tiquisimo
The zipline tours through the forest canopy originated as a commercial venture in Monteverde. There is some dispute about by who and how they were invented. One of the local businesses even has a copyright on the term "canopy tour", which has become the catch all term that many use to describe this adventuresome activity. We won't get involved in this argument.
But we will tell you that this is one of the most fun things you can do during your adventure in Costa Rica. They are scattered all over the country. But I feel that the best ones can still be found around Monteverde.