Heard on the Net: (urban legend per comment below ... but a principle worth remembering.)
When NASA first started sending up astronauts, they
quickly discovered that ball-point pens would not work
in zero gravity. To combat this problem, NASA
scientists spent several years and a $1 million
development project to produce a
pen that writes in zero gravity, upside down, on
almost any surface, including glass, and at temperatures
ranging from well below freezing to over 200 F.
The Russians used a pencil.