In a mixing bowl whisk together honey, soy sauce, olive oil, garlic and red pepper flakes if using until well combined.
Place shrimp in a gallon size resealable bag or a shallow dish. Pour marinade over shrimp, seal bag while removing excess air. Rub marinade over shrimp and transfer to refrigerator and let marinate 30 to 60 minutes.
Note if using wooden skewers soak in water at least 30 minutes so they don't burn up.
Preheat a grill over medium-high heat to about 400 degrees.
Thread shrimp onto skewers. Clean grill grates and brush with oil.
Place shrimp on grill and cook through, about 2 minutes per side.
Sprinkle with green onions or parsley if desired and serve.