Usually water, but because I am a childish freak, I still really like a lot of sugary caffeinated stuff (really into Dr Pepper for some reason), but I am kind of getting less and less into it and will probably be almost exclusive to water next year.
When Halo games come out, I go nuts and buy tons of the Halo branded drinks, because that is the kind of person I am. As Barry pointed out, I am a pretty big loser with it, the worst recent thing I did was buy a bunch of Pepsi that had a big SEGA logo on it, but it was for the Iron Man 2 game. :|
I always wanted to try Jones Soda.