Flap meat, also known as sirloin tip, is one of the most tender and flavorful cuts for your dollar. The key is to use a great spice rub for flavor and to slice thinly against the grain for tenderness.
'flap meat' on Serious Eats
I first knew flank steak by its local New England name of sirloin tip. Go to any old school dive or tavern with a menu, and you're bound to run into them, cut into cubes, stuck on a skewer, and grilled over an open coal fire, just like they do at Santarpio's over in East Boston. When grilled right, they're tender, juicy, take on marinades extremely well, and have a robust beefy flavor that a lot of other cuts-for-kebabs lack. That and they're cheap.
These are the butcher's cuts. These are the cuts that chefs love to use because not only are they inexpensive, but they've got character. Here is a brief overview of my five favorite inexpensive steaks: the hanger, the tri-tip, the short-rib, the skirt, and the flap meat.