#1 - Sit out in Central Park at night -- They have live musicians. Grab a seat among the trees after dinner and order a drink and enjoy. If you do nothing else on this list, do this one!
#2 - Attend the guacamole class at Sabor. For $20, they show you how they make their awesome guac, plus they'll serve you margaritas and feed you lunch. They'll also give you the recipe to take home. I've made it several times since the cruise.
#3 - Have a drink in the Rising Tide Bar. It's a place on the promenade. Every half hour it rises up three decks. Yes, it's a gimmick, but it's cool.
#4 - Listen to the Latin music and have a mojito in Boleros. It's on the promenade right across from the karaoke bar (Karaoke bar is really fun, too)
#5 - See the Aqua Show. If you haven't reserved it, make a reservation. It runs on only the first two nights and features high divers. On the nights when they're not performing the show, walk by the theatre and see the dancing fountains -- similar to what you'd see at Bellagio.
#6 - Park Cafe - On boarding day, skip the Windjammer buffet and head up to Park Cafe in Central Park. You'll find salads, and sandwiches. So good that you'll be back for more on other days.
#7 - Do the zipline. It's only about six seconds, but, what? Are you not going to do it?