Gotten from Tumblr. Source hidden to protect the guilty.
This is one that seems to be making the internet rounds lately.
American astronauts actually started off using pencils when they first went into space. But they quickly realized that the higher oxygen content in the capsule make the highly flammable carbon in the graphite of the pencil even more... flammable. Which isn't really a good thing.
The tip of the pencils would also break off and float though the cabin. This was more than just a small hazard from potentially inhaling a small piece of sharp graphite -- the bits of pencil got into the equipment and caused shorts.
NASA didn't actually invest any money into the Space Pen -- it was done by Paul C. Fisher, with his own money.* He was successful, creating the Fisher Space Pen used today by both the Americans and the Russians. ** He sold his pens to the Space Agencies for $2.95 apiece.