Melt the butter in a large skillet over medium heat. Stir in the garlic, onion, Cajun seasoning, cayenne pepper, and red pepper flakes; cook and stir until the onion has softened and turned translucent, about 5 minutes. Stir in the shrimp. Cook the shrimp until they are bright pink on the outside and the meat is no longer transparent in the center, about 5 minutes. Drain and discard any excess grease. Set aside.
Mix cream cheese, liquid smoke, and lemon juice in a large bowl. Stir in the shrimp and 1/2 cup of pecans, mixing until evenly distributed. Roll the mixture into a ball. Cover with plastic wrap and refrigerate until slightly firm, about 30 minutes. Mix the parsley with the remaining 1/2 cup of pecans in a bowl. Roll the cheese ball in the parsley mixture until the ball is covered. Cover and refrigerate the cheese ball until completely firm, about 2 hours.