These are the things you need to look out for in New York City.
The most dangerous are the folks on bicycles - the racing types who speed around the outer ring of Central Park and the delivery boys (and they are all boys/men) paying no heed whatsoever to the traffic lights. I know that New York taxi drivers have a certain reputation, but they very rarely run even yellow lights. The guys on bicycles, however, zip around corners and through cross-streets with no regard to cars, people, or animals in their paths.
Then, there are all the umbrellas which pop out in force during a rainy period. The sidewalks are already packed with people; give 'em each an umbrella and Whoa! Nelly! Throw in a clueless tourist or two, and you may as well put on armor and goggles to avoid some serious poking. Dangerous!
The third thing isn't so dangerous, but it is irritating: air-conditioner drips. See, New York has - for the most part - not discovered central air conditioning. So every building built before 1980 has a slew of AC units hanging out of its windows. And they drip down, down, down splat! on my head. There I am, minding my own business, walking down the sidewalk and a big ol' drip of water (several, since I walk a gauntlet of AC unit buildings) hits me. Now, I could walk around with an umbrella, but that adds real danger (see above).
Don't say I didn't warn ya' -