Give the shrimp a quick rinse under cold water, then dry them well with paper towels.
Place the shrimp in a mixing bowl and season with chili powder, salt, and pepper. Toss everything together until evenly coated, then let the shrimp sit for about 10 minutes to soak up the flavor.
Set a skillet over medium-high heat and add a little olive oil. Once hot, cook the shrimp for 2 to 3 minutes on each side, or until they turn pink and are no longer translucent in the center.
While the shrimp cooks, heat the tortillas in a dry pan or microwave just until warm and flexible.
Build each taco by layering shredded cabbage, cooked shrimp, avocado slices, and chopped cilantro onto the tortillas. Finish with a spoonful of sour cream mixed with fresh lime juice.
Serve right away with extra lime wedges on the side for squeezing over the top.