I had never put avocado in a smoothie before, but I was glad when this turned out to be delicious! The butter avocado flavor seemed to amplify the berries and even make the smoothie a little less tangy (and therefore, a little more delicious in my opinion).
plain Greek yogurt
frozen mixed berries (or ice)
Place all ingredients in a blender, with the lime juice, milk and yogurt on the bottom. Pulse until smooth.