Heat a griddle over medium-high heat.
In a large bowl, combine the shrimp, olive oil, garlic powder, 1⁄4 teaspoon of salt, and pepper. Mix until the shrimp are coated thoroughly.
In a medium bowl, mix together the avocado, bell pepper, tomato, onion, and lime juice. Sprinkle with the remaining 1⁄4 teaspoon of salt. Set aside in the refrigerator.
Place the shrimp on the hot griddle, on their sides. Cook for 2 to 3 minutes. Flip, and cook for another 1 to 2 minutes. Remove the shrimp from the griddle.
Plate with the avocado salad to serve.