vodka and tonic water for me, I don't like vodka with soda, the fizz ruins the taste IMO. Now C. Morgan and coke(the soda) is another story. But if you are going to mix vodka with anything other than tonic water, use the cheap stuff, you won't be able to taste the difference, and it will save you a penny or two. If you like to drink flavored vodkas straight on ice, you can make your own which I think tastes better than what you can buy anyway. Just do a google on how to do it.
P.S. Be careful drinking vodka and Red Bull, it is very easy to overdose on caffiene while drinking it. It is actually a quite common occurance, especially if you drink coffee, tea and soda throughout the day.