standard mixes for me:
1). Apple/Orange - when you think you need abit more Vit.C. due to
shortage of veges in your meals
2). Watermellon/Orange - when you want some Vit.C., but also the
refreshness and sweetness (not sourness) of the watermellon
3). Honeydew/Apple - when you need some alternate flavour, and
sweet-smelling flavour of honeydew and fiber
4). Watermellon/Papaya - seriously, does not taste as good as the
above 3, but provides good fiber, if you lack veges in meals and
feeling constipated. Again watermellon refreshes. 
