In a small bowl, use the back of a fork to mash the avocado until mostly smooth. Stir in the lime juice, garlic, and salt until everything is well combined.
Warm a dry skillet over medium heat. Once hot, toast the tortillas for a minute or two on each side, just until they’re lightly browned around the edges and heated through.
In a skillet over medium heat, heat a bit of oil. Add the shrimp in a single layer and cook for about 2 minutes per side, just until they’re pink and cooked through.