The space pen versus pencil is a myth perpetuated by people on the Internet who don't know what they're talking about.

http://i.imgur.com/un3H3EN.jpg

http://en.wikipedia.org/wiki/Space_Pen

I thought of the space pen/pencil anecdote as well, but that story isn't accurate, so I like this one better (even if it didn't actually happen).

The pen/pencil thing has the weakness that pencils release small particles and are thus kind of sketchy in low-gravity environments.

Yeah. You could just use a grease pencil or thin crayon though.

Nice sketch pun.