1) Remove the leaves from half of each rosemary sprig. Reserve the sprigs to use for skewers. Chop enough of the leaves to make 1 1/2 teaspoons (reserve the remaining leaves for another use). Combine the olive oil, lime juice, garlic, coriander, chilli powder and chopped rosemary in a medium bowl. Season the marinade with salt and pepper, to taste. Add the shrimp and toss until coated. Let stand for 5 minutes. Skewer 2 shrimp onto each rosemary sprig.
2) Heat a large, wide griddle (or comal) over high heat. Add the skewers and cook for one minute per side, or just until the shrimp is cooked through and turns pink. Do not overcook. Transfer to a platter, garnish with the lime wedges and serve immediately.
Cook's Note: Use the exact same marinade on chicken breasts and whole chickens for roasting. It's also great on any white fish fillet; just add a couple of tablespoons of butter to the pan drippings after the fish has been cooked and removed. Drizzle the sauce over the fish and serve!