Want to shop? Head for 5th Avenue. Make sure to stop in at Tiffany's to see what a $750,000 engagement ring looks like. [Sparkle doesn't even begin to describe how it looks. Try and wrap your head around that much money sitting on someone's finger.]
Want to experience sensory overload? Go to Times Square and stare up at all the neon on the skyscrapers, while thousands of people pass around you. For a $10 you can even get your name and a message up on the neon sign outside M&M World.
Want some exercise? Go for a jog in Central Park, but watch where you are going because the horse drawn carriage rides are all over the place.
Want to be lazy? Grab a 24 hour ticket for the double decker tour bus that winds its way around Manhattan, featuring a tour guide explains the buildings (Empire State, Chrysler, etc.) and neighbourhoods (Greenwich Village, SoHo, etc.). The great thing about this option - especially if you don't have a lot of time - is that you get to see a lot of Manhattan in a relatively short period of time. You can hop on and hop off at each stop so if you want to explore, go for it. The next bus is only minutes away.
I did all these things, but started in the most unlikely place: St. Patrick's Cathedral


Then the doors were opened, the pipe organ pounded away and we headed out onto 5th Ave. to join the thousands of shoppers, while a member of the Salvation Army rang his bells and sang out hoping to get people to stop and make a donation at the street corner.
For everything that New York has to offer, listening to Christmas carols in St. Patrick's Cathedral was easily the highlight of my trip and one of my top three travel memories, ever.