Heat your grill and allow the grill to heat up to 500 degrees Fahrenheit.
Meanwhile, rinse the uncooked shrimp under cold water, drain, and place in a mixing bowl. To the shrimp, add lemon juice, sunflower oil, chopped garlic, garlic powder, salt, and pepper and allow to marinate while the grill heats up, for at least 15 minutes.
For a foil wrap, add the shrimp to a foil pack and seal the top. Add the foil pack to the hot grill, and grill for 10 minutes or until shrimp are opaque pink and cooked through.
Once the grill reaches temperature, open the lid, and add the shrimp to a grill basket or grill pan/cast iron skillet, cook the shrimp on the grill pan or basked for 2-3 minutes on one side (smaller shrimp will cook quicker), until opaque pink, the using a large spatula, flip each shrimp, and cook on the other side for an additional 2-3 minutes until cooked through and opaque pink.
Remove shrimp from grill, and serve!