In a large bowl, whisk together honey, mustard, garlic, chili powder, cumin, paprika, salt, and pepper.
Add flank steak to honey-mustard mixture and coat steak evenly. Allow to marinate for at least 1 hour.
Heat grill to medium-high heat. Grill steak for 7-10 minutes per side, or until desired doneness is reached.
Remove steak from grill and let rest for 10 minutes before slicing.
Slice steak into thin strips.
Heat tortillas in a dry skillet over medium heat for 1 minute per side.
To assemble tacos, place steak strips in warm tortillas and top with desired taco toppings. Serve with honey-mustard glaze.