When I saw someone's layout posted here with white writing that looked so clean and crisp, I asked what type of pen she used. She responded that it was the Signo uni-ball. I had to have one.
It writes so smooth and dries quickly (not instantly - so watch out you don't smear). I've only have the chance to use it a few times so far, but as long as it works this well until it's empty, I'll be buying more.