Prepare the Glass: Rub a lime wedge along the rim of a rocks glass and dip it into coarse sea salt. Fill the glass with fresh ice.
Combine Ingredients: In a cocktail shaker, add the reposado tequila, fresh lime juice, and agave nectar.
Shake Vigorously: Fill the shaker with ice and shake vigorously for 15-20 seconds until well chilled.
Strain: Strain the mixture into your prepared rocks glass over the fresh ice.
The Float: Gently pour the Grand Marnier over the top of the drink so it floats.
Garnish: Add a fresh lime wheel to the rim and serve immediately.