In a large bowl, combine balsamic vinegar, olive oil, garlic, cumin, chili powder, salt, and pepper.
Place steak in marinade and let sit for at least 30 minutes, or up to overnight.
Preheat grill to medium-high heat.
Grill steak for 5-7 minutes per side, or until desired doneness is reached.
Remove steak from heat and let rest for a few minutes before slicing.
To assemble tacos, place steak slices in tortillas and top with desired toppings.
Drizzle with balsamic glaze and serve.