5. Witness Manhattanhenge
What other city has its own very special solstice, much less two of them (usually in May and July if you're not familiar/didn't notice the perfect alignment of the sunset with our East-West street grid)? (Okay, Boston has something, but it happens in a stuffy MIT corridor. If you witness that you'll catch nerditis! Ew!)
6. Use your friend Jen's inspiring triumph of the spirit as an excuse to party on a Sunday
The New York Marathon -- it's so good when other people run it.