Pre-heat oven to 375F to warm tortillas. Place tortillas in foil to warm them all at once.
If you're using wooden skewers to grill the shrimp, it's a good idea to soak them in water for 10 minutes so they don't splinter. I simply wet a piece of paper towel and wrap the skewers in it. You should have enough shrimp to make four skewers.
If shrimp are frozen, place in a colander under cool running water until they're thawed. Peel and devein if necessary. Take the tails off if you don't want to do it after grilling them.
Prepare the shrimp basting oil by adding olive oil, garlic, and smoked paprika to a small bowl, and stirring until combined.
Make the guacamole by mashing together the avocados, garlic powder, lime juice, and salt and pepper. Set aside.
Prepare the garnishes as needed (chop tomatoes, onions, and cilantro, cut lime, etc.).
Once your skewers have soaked for 10 minutes, thread the shrimp on them (make a C-shape by poking the top and bottom of the shrimp through the skewer).
To grill the shrimp skewers, BBQ them on high heat for approximately 2-3 minutes per side or until they're cooked but not overdone (you'll have to adjust based on your BBQ). When you first place the skewers on the BBQ, immediately baste the top of the shrimp skewers with the basting oil, then when you turn them over, baste them again. I recommend a silicone baster as it will withstand the high temperature.
Remove to cooked shrimp from the skewers using a fork. Remove tails from shrimp if you didn't prior to grilling.
Assemble tacos by adding shrimp, guac, sour cream, onion, tomatoes, and cilantro to the tortillas. Enjoy immediately with more fresh lime juice.