First one that comes to mind was our trip to Hanoi. We boarded an old Soviet helicopter for a tour over Halong Bay and then inland to Hanoi. Then we saw Ho Chi Minh's Mausoleum along with a number of other sites, the Hanoi Hilton, and did some shopping while dodging motorcycles everywhere. On the way back to the ship by bus, we saw plenty of other sites such as a family of six on a single motorcycle and a live pig tied down on the back of a motorcycle.
Another highlight was taking a waverunner all the way around the Bora Bora lagoon. Of course, the helicopter tour of Bora Bora was also fantastic.
I always have to get off the ship, even if I have been there countless times. I may only poke around near or on the pier, but gotta check it out!
Favorite excursion was jungle safari in Barbados. Amazing scenery. Second one that comes to mind is the botanical gardens in Martinique. beautiful and educational.