Rub a lime wedge around the rim of a cold margarita or rocks glass. Dip the rim into a shallow dish filled with salt.
Fill a cocktail shaker halfway with ice cubes. Pour in the tequila, triple sec, lime juice, agave syrup, and grenadine.
Shake well until the outside of the shaker feels cold. Place ice into your prepared glass and strain your drink into it. Add a lime wedge on the rim as an optional garnish.