One of my personal favorites, Durban Poison offers a nice energetic high. Your head feels buzzy from the moment of your first inhale. The strain really makes you productive and ready to work.
This is one spectacular strain. Once smoked I usually get in bed, on my laptop and start writing. This strain offers a very sweet mellow high that allows you to sink comfortably into your chair. When smoked outside this strain makes the night sky dance wondrously as the stars and moon glow above you.
I favor Sativa's mostly because of their energetic qualities. Mango Dream offers just that, but only for around 20 minutes. After a short period of time the energetic high cruises down to a very mellow sleepy high which gets in the way of productivity. This strain tastes great and feels amazing once smoked. I recommend this to anyone who is looking for a nice "before bed" bud.