Pen that uses blood for its ink
I've gotten much better at having blood drawn and it doesn't bother me now, but I don't know if I could take some of my own. I'd love to feel how well it writes, though.
Only the first minute of this video is worth watching. The rest is just more writing.
Note: This is not me and since there's no proof that's blood (watch the editing), I think this is more of a concept and is using red ink.