2mm glow-in-the-dark graphite! (I've some some 2mm black graphite picks that I really like, but it would be easier to find them when dropped on dark stages if they glowed in the dark. Then again, they're graphite, so I guess they're just gonna be black anyway... :).)
Now I'll stand back to make way for all the people shouting for ultrathin dinosaur toenail plectra ... 8)