One more horror story of mine:
About seven years ago, back in my first year of high school, I recruited some newbies to try out a D&D game. I was running the Dragonlance Key of Destiny.
The PCs had the eponymous Magic Key Artifact in their possession, and had to flee into the city sewers to evade the Dark Knights (one of the major villain groups of Dragonlance).
There were rumors (and evidence found by the PCs) that an Elven enclave was living underground in an ancient temple in the sewers. The PCs went through the sewers, killing many monsters on the way, to get to this safe haven.
We had a Barbarian, Fighter, Ranger, and Wizard in the party. Due to being low level, the melee PCs were kicking ass and a good time was being had by all.
Things took a turn for the worse when he got into the enclave.
The Key of Destiny was an Elven Artifact, and the elves' Wizard leader wanted to help the party find out about the Key's true nature. Out of the blue, the Ranger's player announces that he's going to try to rape her; in front of her guards, the PCs, and within shouting distance of pretty much every elf in the compound.
Due to said player's immaturity, I thought this was a joke in poor taste and ignored him. When he found out that the Dungeon Master wasn't going to let him do this, the player got genuinely angry and acted as though I was "denying" him something.
Fortunately the rest of the group had none of it. The PCs, the guards, and the Wizard overpowered him and tossed him into the sewers to fend for himself. And these sewers were massive, the "roll for random encounters like overland travel" massive.
The Ranger decided that the best option that he could hope for was to go out in a blaze of glory, so he said he would try to find the biggest, baddest monster in the area. After wrapping up the Wizard's Divination session, I rolled for him. He got a pack of Ghouls led by a Ghast.
Even though he got killed and eaten, technically this was what he wanted. The session to him seemed to be more about trying to push the envelope of my comfort level and getting the spotlight on him.
Now that I'm older and wiser, I would have done things differently if I could go back. I'd probably tell him, in an authoritative tone, that this kind of stuff just wasn't done in my games. If he persisted in arguing, I'd show him the door (the game was at my house).
