A bunch of members of my campus's Gamers' Club got together after a meeting to play a 10th level one-shot (one-session campaign) of Dungeons and Dragons 3.5 edition. Our party, mostly pregens (pregenerated characters, or ones created beforehand to speed gameplay), consisted of a paladin devoted to Heironeous (the God of Valor), a cleric of St. Cuthbert (the God of Retribution), a female elven fighter specializing in archery, a 12 year old female rogue, a scout, a barbarian, an enchanter (a wizard specializing in enchantment spells), and a 2-weapon build male fighter.
Because it's standard fantasy convention, we all started in a bar. The paladin and cleric were sitting in one corner near the door, the male fighter in another, the enchanter and barbarian were sitting together in a table in the middle of the room, while the scout, female fighter, and rogue were in the far corner. Scattered around the bar are various NPC townsfolk, as well as several off-duty guards.
Almost immediately, the cleric jumped on the table and starts preaching about the evils of alcohol. This elicited an unfavorable reaction from the male fighter, who threw his tankard across the room. There was a quick exchange between myself (the paladin) and the fighter which resulted in a "Don't do that again." The barbarian, meanwhile, had taken it upon himself to drown out the sermon with a rousing drinking song about ale and whores. This irked the elf, who was being played as a feminist.
Shortly thereafter, one of the observers to the game said, "I'll start the riot by throwing a chair." The DM laughed heartily, thanked him, and then called for an initiative check. Chaos then ensued.
The townsfolk and bar staff scattered. The rogue and scout immediately went into hiding under a table, while the elven fighter shouted, "Women are not objects!" and charged the barbarian, smashing a barstool against his head. In response, the enchanter pulled out a staff of Hold Person and cast it on her. One failed Will save (a reaction roll that allows you to, among other things, escape magical effects), and we now had an angry elf frozen in place The barbarian proceeded to pick up the elf, and use her as a club to kill vipers which the cleric had summoned (if anyone was curious, she did 1d6 damage). Once everyone finished rolling on the ground in laughter, my character jumped on the table and shouted for everyone to calm down and stop fighting. Despite having a 20 Charisma, it seemed I didn't have the force of presence to get the situation under control. During all of this, the male fighter had been using his whip to knock over tankards and break bottles, splashing alcohol everywhere.
On the next initiative, things devolved even more. The scout came out of hiding, and pulled out his bow, firing at the barbarian. He missed by a large margin, and pegged one of the guards in the back. I leapt across the tables to the bar, and started looking for the one who shot the arrow. In my character's eyes, this situation should be handled with as little bloodshed as possible, and the bow had been the most significant lethal force thus far. Naturally, I suspected the scout. I ran across the bar, screaming "Flying Leap of Justice!" and tackled him, attempting a pin.
Next round, the guards were finally getting some semblance of control. They had gotten the barbarian to drop the elf, the enchanter to release his spell, and the cleric to stop summoning vipers. The male fighter, however, was left to his devices. He activated his +2 Flaming Scimitar, and lit the alcohol he was spreading on fire. That's right. He was planning on burning the entire place to the ground. I then dashed across the bar and tackled him, because fire is far more dangerous than arrows.
The rogue, scout, and elven fighter didnít like what was happening, and all three made a break for the windows and escaped, with the barbarian in short pursuit. When they got outside, they saw a guard troop advancing towards the bar, ready for battle. Meanwhile, the cleric summoned a small Water Elemental around the fighter to keep him from igniting anything further, the enchanter attempted (and several tries later, succeeded) in charming one of the guards, and I and the guards were attempting to take down the renegade. Just as the captain of the guard arrived, we brought him to -5 HP (in D&D, when a character is reduced to negative HP they are considered dying and lose health each round, and are officially dead when they reach -10). I stabilized the fighter (make it so he's no longer losing hit points) and handed him over to the captain as our cleric explained the situation.
Then, after two hours of silliness, the party made it out of the bar, found the plot hook of the one-shot, and eventually started working together. If every bar scene played out like this one, though, I doubt it would be considered a trite gaming convention.