Fin.

Shark fin, that is.  If you haven't eaten it, then eat it once, and enjoy yourself, and then research how they harvest it, and don't eat it again.  But give thanks to the Cantonese for figuring out how to make such a relatively inedible part of a relatively inedible fish so darn tasty.  Because love or hate the environmentalist considerations around it - shark fin is really darn tasty.

Here are some shark fin joints (and shark fins) around Chinatown.  Note the prices for the big ones (3500 baht is about $100 USD) - there's a reason you pay - it's tasty, the big ones are rare, and it's hard to tell the real fins from the fake ones, so you pay for quality and for famous restaurants.  The ads for "300" or "500" baht shark fin soup - not only is that a fair bit for a meal in this town, but you're going to get a little tiny bit of shark fin for that amount.  Yup, when it comes to shark fin, you get what you paid for.

Oh, and go eat some shark fin.

Fin.