Flank Steak is cut from the belly of the cow. It is often used in a London Broil, a dish that doesn't come from London. Flank steak is one of the less expensive steaks. Because it is fairly tough it is often braised or marinated. It is often used in Chinese stir-frys.
In addition to the wines mentioned in our food pairing table you might consider a French Bordeaux wine or a Cabernet Sauvignon.