To make the marinade, in a small saut pan over medium heat, melt the butter. Add the garlic and cook, stirring occasionally, until soft, 2-3 minutes. Remove from the heat and add the remaining marinade ingredients. Stir and allow cooling at room temperature. Using a sharp knife split open the back of each shrimp and devein it. Place the shrimp in a large, resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade, place in a bowl, and refrigerate for 20-30 minutes. Remove the shrimp from the bag and discard the marinade. Grill over direct high heat until the shrimp are just opaque in the center and firm to the touch, 2-4 minutes, turning once halfway through grilling time. Remove from the grill and serve warm or at room temperature with rice.