In a large skillet, heat olive oil over medium-high heat. Add sliced onions and bell peppers, and sauté for about 5 minutes until they start to soften.

Add the shrimp and fajita seasoning to the skillet. Cook for an additional 5 minutes, stirring occasionally, until the shrimp are pink and cooked through.

Warm the flour tortillas in a separate pan or microwave.

Serve the shrimp and vegetable mixture on the tortillas and top with sour cream, shredded cheese, guacamole, and salsa as desired.