In a mixing bowl, add all ingredients except chicken or shrimp and whisk well.
Cut chicken breasts into cubes, or if you are using shrimp, peel and devein shrimp
If using chicken, add to a resealable bag, then pour in half the marinade. Allow to marinate for at least 2 hours.
Reserve remaining marinade for a dipping sauce.
Remove chicken from bag and skewer on soaked skewers. Prepare grill and cook until chicken is at least 165 degrees. Remove and pull off skewers.
If using shrimp, skewer shrimp and then brush with marinade. Grill until shrimp is opaque and firm, brushing with marinade often.
Serve with either your favorite taco condiments or as a main course with your favorite side items.