If using wooden skewers, soak them in water to prevent burning. Place the shrimp in a wide shallow bowl and set aside.
In a small bowl with high sides, combine olive oil, garlic, jalapeno, brown sugar, smoked paprika, chili powder, garlic powder, onion powder, cumin, kosher salt, and black pepper. Use an immersion blender to blend until smooth, or use a food processor or blender.
Pour the marinade over the shrimp and gently stir to coat evenly. Cover and refrigerate for 2 to 3 hours, folding gently about halfway through.
If desired, drizzle tequila over the shrimp and gently fold to combine. If using skewers, thread the shrimp onto skewers, placing a folded slice of lime between each shrimp.
Heat the grill to medium-high. Ensure the grates are clean, then oil them well. Place the shrimp on the grill and cook for 3 to 4 minutes per side, or until the shrimp are no longer translucent and have a nice char. Adjust cooking time based on the size of the shrimp.
Transfer the grilled shrimp to a platter, sprinkle with chopped cilantro, and serve with fresh lime wedges for squeezing over the top.