In a medium bowl, mash the avocado with a fork. Stir in lime juice, garlic powder, salt, and pepper until well combined.
Add the diced tomato, red onion, and cilantro to the avocado mixture, and gently fold to combine.
Lay the flour tortillas flat on a clean surface. Spread half of the guacamole mixture evenly over each tortilla.
On top of the guacamole, layer the cooked shrimp and sliced steak evenly.
Add shredded lettuce on top of the meat. If desired, add a dollop of sour cream.
Carefully roll each tortilla tightly, starting from one end and tucking in the sides as you go.
Slice each wrap in half and serve immediately, or wrap in foil and refrigerate for up to 2 hours before serving.