I've always found flank or skirt steak to be an incredibly underrated cut of meat. Yeah, it's a bit tough, but it's got such a great flavor. Here's a marinade out of the John Folse Encyclopedia that not only has an awesome flavor, but does a great job of tenderizing the steak.
1 flank steak (about 2 pounds)
1/4 cup vegetable oil
1/4 cup balsamic vinegar
1 tbsp Louisiana hot sauce (I used Tabasco's Smoked Chipotle and found it an excellent addition)
1 tbsp Louisiana cane syrup
1/4 cup minced garlic (I used some leftover puree that I had on hand from a crawfish boil)
1/2 tsp crushed red pepper flakes
1/4 tsp cracked black pepper
2 tbsp chopped thyme
2 tbsp chopped basil (I used dried in both cases, it came out fine)
1/8 tsp ground cloves
2 tbsp firmly packed brown sugar
Salt and Creole seasoning to taste
1. Trim the steak to your taste and then with a paring knife, cut 1/4-inch slits at 1-inch intervals across the top of the steak. Place in pan with a nice lip.
2. Pour the oil, vinegar, hot sauce and cane syrup over the steak, and use your hands to massage it in to the meat well.
3. In a small bowl combine the garlic, peppers, herbs and sugar. Mix well and rub the mixture all over the steak, coating well. Cover the pan and allow the steak to marinate at room temperature for at least four hours.
4. Meanwhile, heat your grill. I used charcoal, but I'm not a fuel snob. Cook it over whatever works best for you. On charcoal, place the meat right over the hottest part of the coals and cook it to your desired temperature, flipping once. You should have medium-rare after about 5 minutes on each side.
Allow to rest for a good 20-30 minutes before serving. This makes for great fajita meat, as skirt steak tends to. Serves about 6 people.