It may sound a little weird, but the blueberry avocado smoothie is fantastic! The avocado doesn't really add much taste, rather it makes the smoothie deliciously creamy. 

All you need for this recipe is an avocado, blueberries, a banana spinach, water and ice. 

1 cup water
1/2 ripe avocado, pitted and sliced
1 cup fresh (frozen will work) blueberries
1 banana
2 cups spinach
1 cup ice

and if you like your smoothies a little bit sweeter
1 tbsp agave or honey