Heat the oil in a large frying pan over medium heat. When it shimmers, add the onion and garlic, season with salt, and cook until translucent, about 8 to 10 minutes.
Add the shrimp and cook until they turn pink, about 3 minutes. Remove the pan from heat, add the tequila, and scrape the bottom of the pan to incorporate any browned bits. Return the pan to heat. (If you want, carefully tilt the pan to ignite the tequila.) Simmer until the alcohol smell has cooked off and the shrimp are fully cooked, about 3 minutes.
Remove from heat, stir in the lime juice, and season with salt and pepper. Taste, adjust the seasoning as necessary, and serve with extra lime wedges, pico de gallo, and guacamole as desired.