In a medium bowl, combine the shrimp, olive oil, chili powder, cumin, garlic powder, salt, and pepper. Toss until the shrimp are evenly coated.
Heat a large skillet over medium-high heat. Add the seasoned shrimp and cook for 2-3 minutes on each side, or until the shrimp are pink and cooked through.
While the shrimp are cooking, warm the tortillas in a separate skillet or microwave until pliable.
To assemble the tacos, place a few shrimp on each tortilla, then top with shredded cabbage, avocado slices, and chopped cilantro.
Serve with lime wedges and a dollop of sour cream or Greek yogurt, if desired.