In a large bowl or ziplock bag, mix together garlic, lime juice, tequila, Olive Oil, black pepper, cumin and salt until combined. Add chicken breast pieces, and toss until evenly coated. Cover or seal, and refrigerate for 30 minutes, or up to 8 hours.
Preheat grill to medium-high heat.
Remove chicken from bag, and discard the leftover marinade. Thread chicken onto skewers*, then season the chicken with a few extra pinches of salt and pepper. Place skewers on the grill and cook for 6-8 minutes, turning once, until the chicken is cooked through. Remove and serve immediately, garnished with fresh cilantro** and drizzled with Lime Olive Oil if desired.
*If using wood skewers, be sure to completely soak them in water for at least 10 minutes before threading on the chicken. This will help prevent them from burning.
Recipe adapted from Gimme Some Oven.com