Watermelon and Tequila are an amazing combination and not used in enough cocktails!
1 Jalapeño pepper slice
3 Watermelon cubes (about ⅓ cup)
2 oz Silver tequila
3⁄4 oz Fresh lime juice
3⁄4 oz Agave syrup
HOW TO MAKE THE TEQUILA MOCKINGBIRD COCKTAIL
Muddle the jalapeño and watermelon in a shaker. Add the remaining ingredients and ice, and shake until well-chilled. Fine-strain into a rocks glass over fresh ice.
From Liquor.com for more wonderful cocktails