Preheat grill to medium-high and place the limes flesh side down on the grill. Cook for 5 minutes or until real nice char marks appear, set aside. Peel pineapple and cut into 4 large pieces lengthwise, cutting around the core, then cut into eights. Skewer the pineapple spears and grill on each side for 2-3 minutes or until nice char marks appear. Halfway through the cooking process, squeeze a good amount grilled lime juice over the pineapple, this will keep the pineapple moist and infuse that charred lime flavor.