This isn't exactly me being a dick player, but I have a great story from a roleplaying session about two weeks back.
I was GMing this modern campaign using Fuzion (and for those unfamiliar with the system, you take character disabilities ala GURPS), and two of the party members had unknowingly taken opposing views on prisoners. Both had taken the most extreme penalty for their ideology: one to finish every fight he starts (to the death), and the other for a sense of honor to never finish a downed opponent, among other things.
The fight started with one PC trying to snipe with a bolt action rifle from some ridiculous distance, missing and alerting the guards, and in return, taking two rounds from an AK right to the stomach, killing him. The rest of the PCs called out to surrender. When they got close enough, one charged the closest guard with a knockout punch.
After shooting a few more guards and finishing the fight victoriously, the party then went to discuss what to do with the knocked out guard. The punching character immediately went to choke him to death, while the honorable character shouted in protest. The honorable PC then drew his pistol and told the puncher to step away from the guard. The puncher then charged the honorable PC, going for another knockout. He missed, and took two shots to the foot (luckily, he could have easily been killed). He then connected on his next turn, sending the honor bound character to the floor.
The other members of the party then immediately went to the defense of the honorable PC, knowing he'd be choked out while unconscious if left to the punching character. One member charged the punching character, pistol whipping him into oblivion (he only had like 2 knockout hit points left).
The puncher's player later asked me if he could change his disabilities, and for the sake of the party, I agreed.
So yeah, not really being a dick as much as acting out their characters, but an entertaining story nonetheless.
