Offal, "variety meats" - Sweetbreads, kidneys, chitlin's, pork Farcis (face), etc. etc. etc. where and that's the best?
What I know:
Sweetbreads: Craft (good, small), Gramercy, Prune (larges, best), Babbo (decent, but with orange rind), Blue Ribbon Bakery (a bit greasy.)
Lambs Brain: Le Cirque 2000 (Thursday(?) special in Pot Au Feu "Traditionnel" or Bollito Misto)
Pieds de Porc Farçis aux Truffes Noire with Crushed Herb Potatoes and Sautéed Spinach - Saturday special at le Cirque 2000
Pigs Foot: Babbo (barely recognizable), Les Halles (better)
Kidneys: God, someone find me a good kidney! I'll even wear a tie and jacket if necessary.
You can get some of these in Chinatown, but you have to know what they look like and what to do with them. You can get sweetbreads at Ottomanellis. You can get chicken hearts and some other stuff from the butcher at Union Square in the Southwest corner. You can get pig's feet, goat, tripe (featheres and honeycomb)in Chinatown and at the meat stores on 42nd and 9th (which as a great selection of pork shoulders, btw) and at 10th and 14th; they latter also has 10 lb buckets of frozen chitterlings. But you better have a load of friends to finish off a 10 lb bucket of chitterlings, let me tell you. :-)
Where else serves a good variety meat?