To prepare salsa, combine first 6 ingredients, stirring well with a whisk. Stir in onion, habanero, and tomatillo. Cover and let stand at room temperature 30 minutes.
To prepare shrimp, peel shrimp, leaving tails intact. Starting at tail end, butterfly each shrimp, cutting to, but not through, underside of shrimp. Combine 1 tablespoon of lime juice, 2 teaspoons oil, garlic, and dash of salt in a large bowl. Add shrimp; toss well. Cover and marinate in refrigerator 10 minutes.
Place shrimp, cut sides down, on grill rack coated with cooking spray, and grill for 5 minutes or until shrimp is done, turning once. Serve with salsa.