Marinate shrimp overnight with 1/4 cup lime juice in a large bowl covered with plastic wrap. Drain shrimp.
Heat shrimp in a microwave-safe bowl until they are bright pink on the outside, about 6 minutes. Allow shrimp to cool.
Bring a large pot of lightly salted water to a boil. Cook cellentani in the boiling water, stirring occasionally until cooked through but firm to the bite, 12 minutes. Drain, then rinse with cold water until cool.
Mix shrimp, pasta, avocados, grape tomatoes, red onion, and cilantro in a bowl.
Whisk olive oil, 1/4 cup lime juice, garlic, Worcestershire sauce, dry mustard, salt, and black pepper in a bowl until dressing is well mixed.
Pour dressing over shrimp mixture; toss to coat. Chill before serving.