Try this with a reposado tequila for a little depth of flavor.
2 lime wedges plus juice of 1 lime
Kosher salt (for glass rim)
1 1/2 oz. tequila
1/2 oz. Cointreau or triple sec
1 cup ice cubes
1. With 1 of the lime wedges, rub rim of chilled martini or margarita glass. Pour salt onto plate, and press rim of glass into it, turning gently until rim is evenly but lightly coated. Shake off excess.
2. In a cocktail shaker, combine tequila, Cointreau, lime juice, and ice cubes. Shake well. Strain into prepared glass. Garnish with remaining lime wedge and serve.