Coney Island is the best for everything - the beach, the rides, the beer - but mostly for the Skee Ball. It's incredibly addicting, affordable and satisfying (depending on your aim).
Chillhouse is awesome. It's a great place to chill out while waiting to meet a friend, read a book, or get your nails done. This all-in-one cafe has made it easy for the girl on the girl that needs some self-care time.
An hour away from NYC, there lies a summer camp on a pristine lake which was abandoned 15 years ago. I cant tell you where this is, but some research can lead you to the right place.