In a medium bowl, combine shrimp with olive oil, chili powder, cumin, garlic powder, salt, and pepper. Toss to coat evenly. Let marinate for at least 10 minutes.
While shrimp marinates, prepare the lime crema. In a small bowl, whisk together sour cream, lime juice, minced garlic, and salt until smooth.
Heat a large skillet or grill pan over medium-high heat. Add the marinated shrimp in a single layer. Cook for 2-3 minutes per side, or until pink and cooked through.
Warm the tortillas according to package directions (in the oven, microwave, or on a dry skillet).
Assemble the tacos. Spoon the cooked shrimp into the warm tortillas. Top with shredded cabbage, cilantro, and diced red onion.
Drizzle with lime crema and serve immediately with lime wedges.
Notes
Adjust spice level to your preference by adding more or less chili powder. For a spicier crema, add a pinch of cayenne pepper.