I drink mostly Iced tea, If I drink soda though it's usually Coke. I like sprite also sometimes. To me pepsi tastes like an open coke that was left out overnight.
I realize I'm a little late to the poll, but what the heck...
I vote for Diet Coke - I count calories (it has zero, and tastes pretty good).
For pure taste, I'll go with Vernors, or Faygo creme soda.