A pen from my collection of pens I always pick up at conferences. Some engineering firms have really good pens.
Are you a pen or pencil person? Spock's is most likely a crayon.
If you have a favorite brand/style of pen or pencil, what is it?
I've always been a big fan of the Pilot G-2 as far as cheaper pens go. I also have a GraphGear mechanical pencil that I really like writing with.