Oh, I have several stories..
We had this one player..we'll call her Blackstarre (for that was her handle back in the old BBS days). She kept getting slightly more and more unhinged until the day she called up (shortly after the Crow was released) and said "guess what! I have Brandon Lee's soul in a crystal." And she was serious. BUH BYE.
We had another guy in a Vampire Dark Ages game who threatened Prince Mithras (for those not in the know, Mithras is a VERY powerful character) and, when Mithras told him to watch his tongue, he grabbed a torch and tried to set the room on fire. Mithras staked his butt fast and ordered that he be taken outside, drained of blood and unstaked (this was a VERY lenient punishment) and the player pouted for a few minutes, then the conversation went something like this..
Player: "I leap into the fire."
Me: "You can't. You're staked."
Player: "I leap into the fire anyway."
Other players: "You can't. You're staked."
At which point the player tore up his sheet and stormed out.
And then we have Ms. Gullible. This poor girl would believe ANYTHING you told her. I told her once that the sky was green and she bought it. Unfortunately she took 4 hours to make a starting character. In Vampire (where a character could easily be made in 15 minutes, tops).
In one other Vampire game (I used to play a LOT of World of Darkness, BTW), we had this guy playing a mortal hunter. The conversation went like this..
Me: "You've gotten a good night's sleep, free of horrible dreams. You wake up."
Player: "I open one eye, what do I see?"
Me: "Uhm. Darkness. it's still 3 in the morning."
Player: "I open the other eye, what do I see?"
Me: "Darkness still."
Player: "I put one foot on the ground. Does anything happen?"
Me: "Other than your foot touching cool wood, no."
Player: "I put my other foot on the ground. Does anything happen?"
Me: "Oh geez. No."
Player: "I sit up in bed. Does anything happen?"
Everyone else: "Shut up and get out of bed."
After we FINALLY get his character out of bed he goes about describing, in painstaking detail, how he carves crosses into each bullet and blesses them. Repeating the description for EACH AND EVERY BULLET.
Funny how his character got mostly ignored for the rest of the session and wasn't invited back...