To the bottom of a cocktail shaker, add fresh pineapple and 2-3 thin slices of serrano pepper. Muddle the pineapple and serrano peppers. Pour in the tequila lime juice, agave nectar, pineapple juice and more crushed ice. Secure the lid and shake vigorously. Pour into prepared glasses. Garnish with more pineapple, lime slice and thin serrano slice.