For marinade, combine tequila, lime juice, soy sauce, TABASCO® Sauce, and black pepper in a large bowl; mix well. Add beef and toss to coat well; cover and refrigerate 24 hours, turning meat occasionally.
Combine all pico de gallo ingredients in a small bowl and mix well; cover and chill for 1 hour. Drain steaks and grill over medium-high heat to desired doneness. Let stand 5 minutes; cut into 3 x 1/4-inch strips.
To make fajitas, heat oil in a large skillet over high heat. Add peppers, onions, and tomatoes and sauté until softened, about 5 minutes. Add beef and cook 5 minutes more. If desired, pour mixture into a preheated cast-iron fajita pan and serve sizzling.
To serve, spoon meat mixture onto flour tortillas; top with pico de gallo, guacamole, and sour cream.
Makes 6 servings.