Haha, I stumbled this story before I answered the question. But being and engineering major I knew the answer in a heartbeat anyway...

Since the moon has it's own gravity, the pen would fall to the surface of the moon UNLESS it was thrown into space at the speed of the moon's escape velocity.

Physics 324 - Modern Physics for Engineers

"A body is at rest tends to stay at rest, plus there's no gravity"

"The gravity of the moon can be said to be negligible, and also the moon's a vacuum, there is no external force on the pen. Therefore it will float where it is."

"The pen will float away because the gravitational pull of the moon, being approximately 1/6 that of the earth, will not be enough to cause the pen to fall nor remain stationary where it is. The gravatational pull of other objects would influence the pen"

Physics 222 - Second Semester Calculus-based Introductory Physics

"Because moon has gravitation 1/6 of the gravitation of earth the force will be small toward the moon [so it will float away]"

Physics 221 - First Semester Calculus-based Introductory Physics

"It will fall to the earth by force of gravity and by the attraction between the earth and the moon"

"Because the gravitational pull of the moon is much weaker than that of the earth. And object such as a pen is so lite that it will float"

"Because there are no external forces if you let go [it will float where it is]

"External forces that are present on the moon will attract the pen. There isn't gravity on the moon as there is on earth so the pen won't drop."

"Since there is no gravity it will float and fall slowly. It will not fall like in the ground quickly because there is no gravity"

"The force of gravity on the moon is a fraction of the gravity on the earth, so the moon would not be able to attract the pen to inself. Rather, it would only be able to suspend the pen"

"It will eventually fall to the surface of the moon because of the slight gravitational field plus the moment of inertia about the moon. Also with angular momentum being conserved, it must fall. I=MR^2" [We were studying conservation of angular momentum when I gave this quiz]

"The pen will fall to the surface of the moon. As we let go we will introduce some initial enerty into the pen thus putting it in a forward downward motion. Since on the moon there is no force of resistance the pen will fall very slowly towards the surface"

"If you are standing on the moon holding a pen and you let go, it will float where it is. It will not fall to the surface of the moon because a gravitational force strong enough to cause this does not exist. In addition, the pen does not have a lot of external force on it, so it will not be likely to move"

"The pen will fall to the surface of the moon because the moon generates a gravitational field by rotating and the pen must act under this force".

Physics 111 - First semester Non-calculus Physics

"It will float where it is because there is no gravity force on the moon. Also, if you just let go there isno acceleration so it should just float where it is."

"There is no gravitational force on the moon, the pen therefore has no weight so its mass has no effect on 'where it goes'. Plus, you know, there is no wind to blow the pen up there! =)"