In a large bowl, mix shrimp, oil, onion, garlic with fajita seasoning mix.
Heat a large pan over medium-high heat until it smokes hot. Add shrimp mix in the pan and sear. Let shrimps cook until nicely pink on both sides. It will take about 3 minutes. Remove from heat.
Prepare fajitas. Warm each tortilla in a non-stick skillet for about 10-15 seconds on each side. Start the filling by adding lettuce and red onion then shrimps. Top with cherry tomato, sweet corn, guacamole and lime.