The hanger steak is considered a butcher's best kept secret. It comes from the muscle that helps support the diaphragm between a cow’s rib and loin, its just sort of "hanging there" and it does absolutely nothing... as a result its one of the most tender steaks.
The hanger steak is very exclusive, its even rarer than the tenderloin... and frankly, much more interesting.
There is only ONE hanger steak per animal... a 1,200 pound animal that yields 800 of beef, only has one hanger steak of about 16-32 ounces.
Cook it any way you like, but do not overcook. You are looking for a nice medium... the hanger is a bit tricky, too rare and it will be a bit slimy, too cooked and it will lose its tenderness.