Run a lime wedge around the rim of a cocktail glass. Dip into the lime sugar, shaking off excess. Fill with ice.
In a shaker, muddle the lime juice, mint leaves, agave, and pineapple juice/chunks - if using chunks, muddle until juicy and crushed. Add the tequila, mezcal, and Cointreau. Fill the shaker with ice and shake until cold. Strain into the prepared cocktail glass and garnish with a pineapple wedge and mint leaves, as desired.
Notes
*Lime sugar: On a shallow plate, toss together 3 tablespoons of sugar with 1 tbsp lime zest.