Place an oven rack about 6" from the top and preheat the broiler to high. Line a baking sheet with parchment paper for easy cleanup.
Thread the shrimp onto wooden skewers, alternating with pineapple chunks.
Season:
In a bowl, combine the olive oil, the juice from ½ of a lime, the grated garlic and spices to form a seasoning paste. Add the shrimp and pineapple pieces and toss to coat with the spices. Reserve remaining lime for slicing into wedges and squeezing over the tacos.
Place the skewers on the prepared baking sheet and generously brush with the seasoning on both sides.
Cook:
Place the sheet pan under the broiler for 2 minutes, carefully flipping the skewers with tongs, and cook on the other side for 2 more minutes. Once the shrimp is no longer translucent and have turned pink (no more than 5 minutes total), remove the sheet pan from the oven.
Assemble:
To assemble tacos, place a generous bed of purple cabbage over a tortilla, top with some cilantro, slide the shrimp and pineapple from the skewers onto the taco, and top with guacamole. Squeeze a lime wedge or two per taco and enjoy!