I still carry a "Hipster PDA"[1] around, binder clip and all. Said binder clip came out of a box from the 1970s.

It's immensely useful in a pinch, it's free form, and I can place it flat on a surface and write on it.

And, if I write sensitive information on a card, unlike a regular pocket notebook, I can store it or take a secure photo of it and physically pitch that index card.

Thanks, Merlin Mann[2].

1. https://en.wikipedia.org/wiki/Hipster_PDA

2. https://news.ycombinator.com/user?id=merlinmann