Pokemon "Gray" Version for me - the third version. I've decided to wait until the third version is released. It seems like a better, financially sound decision to me, since each game is essentially the same with the third version having (sometimes) substantially more features/changes added, which is a major plus (the obvious downside is the wait time). If I was able to somehow obtain another version, I'd get Pokemon Black, simply because black looks like a cooler color. Version mascots could play a role in my decision, though...
If I was able to afford all 3 versions I'd probably get them to support the Pokemon franchise (and remove the problem with version exclusives, of course...though that can be remedied by trading anyway), of course... But just getting 1 version makes whichever game you get seem more special, IMO.
Watch when the third version is titled something totally random like "Pokemon Mauve" or something... :\ Really hoping for Pokemon Gray Version, though...