I live in Manhattan and we had a friend in town, so we decided to take advantage of some local tours.

Both are highly recommend:

1. Sailing on a sailboat/schooner on the Hudson River

We took the 8:30pm Adirondack Schooner/Sailboat tour...we arrived to Chelsea Piers (at 18th Street on the Hudson River) at sunset and watched a beautiful sunset over the NJ skyline... Next we went aboard the boat where all seats were waterside and perfect. Included in the sail are unlimited drinks of either champagne, wine, beer, bottled water and soda. While not a party boat, the unlimited drinks were welcome and the glasses remained full. Sailing down the river you will get close to the Statue of Liberty the Brooklyn Bridge, see some of the sites along the way. Very relaxing and great views of the bright city lights. Highly recommend. Aaryn or Eric (can't recall - was our captain and great, knowledgeable) Tickets are ~$45.00 which is a great deal considering the sail and drinks... also found out that you can book online at goldstar.com for $22.00 but not all times are available and we really liked the night sail.
http://www.sail-nyc.com/html/schooners_adirondack_imagine.html

2. Best of Brooklyn Multicultural Ethnic Neighborhood Tour
http://www.newyorkfuntours.com/brooklyn.html

This informative tour lead by our tour guide, Isaac, was just brilliant. We visited real, authentic neighborhoods in the Lower East Side, A Hasidic Jewish neighborhood and a latino neighborhood. Great insights into the way Manhattan is changing and how (some) Brooklyn neighborhoods are keeping their roots and history and people... plus great food stops along the way. We stopped at authentic deli's, bakeries, etc. of neighborhood mainstays -- mom and pop shops that have survived the generations and look and feel like the 1930s or 60s... Good combo of driving (tour guide drives and walking) plus we went to two parks and saw amazing sweeping views of Manhattan from across the river that we would not have seen otherwise. $95.00 is a bit spendy at per person, but worth it. We live but once...

Good for locals or visitors.