Prepare a vegetable juicer (or blender if unavailable). Run the pineapple, limes and cucumber through the juicer, letting all the juices combine. Pour the tequila into a cocktail shaker or pitcher, and then add the juices, ice, agave and salt. Shake or stir vigorously until chilled. Line up 4 tall Tom Collins glasses filled with ice, and pour the tequila cooler over. Serve with straws and cucumber slices for garnish.