Island Beach State Park, NJ
It is one of the few truly untouched beach system in the world. It has the primary dune, secondary dune, and the forest. Yes, there is supposed to be a forest on the beach. Plus, the waves are usually decent. I love the fact there aren't many guarded places because it usually pretty clear.
I go for the beaches that are aesthetically pleasing. Also toping my list are North Wildwood, Harvey Ceders, Cape May(the Point, The Nature Conservancy Beach, and the place that the nun's own-who were ever so kind when I was an intern at TNC and needed a bathroom) and Barnegate Light. All in Jersey.
I'm very patial to my own beaches, and don't really go to anyone else's...although I would like to see Hawaii, Calf, and Austrialia.
Oh yeah, I'm also a Marine Bio dork who goes for all the above over the commericalized beaches.