Make me a drink with mezcal, grapefruit, and lime.

Based on the ingredients you've mentioned—mezcal, grapefruit, and lime—a great choice for you would be the Closing Argument cocktail. This drink features a harmonious blend of lime juice and mezcal, and while it doesn't directly include grapefruit, its flavor profile will complement the smokiness of Mezcal well, especially with the added citrus component.

The Closing Argument cocktail brings together lime juice, mezcal, green Chartreuse, and maraschino cherry, resulting in a sophisticated mix of smoky, sour, and sweet notes. Even though grapefruit isn't a direct ingredient in this cocktail, the citrusy lime will provide a tang that pairs wonderfully with the mezcal's earthy undertones, much like how grapefruit would. It's a well-balanced cocktail that will certainly appeal to your flavor preferences.

If you're specifically looking for grapefruit in your drink, you might try tweaking this a bit or considering another option. You could add a splash of grapefruit juice to enhance the fruitiness, or go for a direct adaptation like the Paloma or Tecate Paloma if you prefer. Both cocktails feature a lovely combination of tequila (which you can substitute with mezcal) and grapefruit juice for a delightful tangy and smoky twist.

Enjoy your cocktail exploration!