Heat vegetable oil in a large skillet over high heat. Add the sliced bell peppers and onion, cooking them while stirring occasionally, until they become tender and lightly charred at the edges. Season with salt and pepper to taste.
In a small bowl, combine the chili powder, cumin, garlic powder, onion powder, smoked paprika, along with salt and pepper. Mix until evenly blended.
Add the shrimp to the skillet with the vegetables. Sprinkle the prepared seasoning mix over the shrimp and vegetables, stirring to ensure an even coating.
Continue cooking for about 4-5 minutes, or until the shrimp turn pink and opaque, indicating they are fully cooked.
Finish by sprinkling chopped cilantro over the fajitas. If desired, garnish with lime wedges. Serve the fajitas with warm flour tortillas and assorted toppings, allowing each person to assemble their own fajitas.