Pencils! Propelling.
Despite having an iPhone, and a laptop at home and at work, I still prefer to use a Filofax for my diary... i know, i know, but I love it. And as I'm always making mistakes, or having to change appointments, my pencil allows me to 'delete' and replan.
I do still have a matching Parker pen and pencil set that I was given for going to high school, almost 30 (!) years ago. I got the piss taken mercilessly for my poncy pen set at the time but I'm still fond of it.