Originally written up in Food&Wine Cocktails 2010 and credited to Jacques Bezuidenhout, a South African bartender working in San Francisco. Originally called for more agave nectar and an aged tequila, but I feel it's more summery as described below.
1 3/4 oz blanco tequila (Tequila Ocho)
1/4 oz scotch (Laphroaig)
1 oz lime juice
3/8 oz agave nectar
Thin lime wheel garnish
Shake ingredients over cracked ice. Strain into a rocks glass over a large ice cube. Garnish with the lime wheel.