I guessed it to be skirt steak. I very flavorful relatively cheap cut.
Skirt steak (which I mentioned above) can be tough if prepared wrong, but it may be the most intensely flavored part of the entire cow. Considering the small yield and the awesome flavor, it's a relative bargain at around ten bucks a pound. But I have to admit the flap meat I had last night, which only set me back a paltry five bucks a pound, may have been the single best all around piece of meat this carnivore ever had.