I've only recently started using Platinum Carbon Black, and I'm quite happy with it. Addresses the one major concern I've always had with fountain pens, which

I've only recently started using Platinum Carbon Black, and I'm quite happy with it. Addresses the one major concern I've always had with fountain pens, which is how illegible everything becomes when exposed to liquid. Not that that's stopped me using fountain pens, and not that it's been a huge problem in practice, but it's nice to have a durable ink.