Add the tequila, lime juice, agave, triple sec and ice to a high-power blender. Blend until the ice is crushed and the mixture is homogeneous, about 20 seconds. Add the avocado and barely blend, about 10 seconds more. The mixture will be smooth and pourable. (Be sure not to overblend, because the mixture will become too thick.)
Use a lime wedge to moisten the rim of the glass. Dip the rim into the coarse salt. Pour the margarita into the glass and garnish with another lime wedge.