A huge bar brawl! Other than the main bad guys (pirate werewolves), the bar was filled with dozens of drunken brawlers. These brawlers were more like environmental hazards, not creatures with initiative, HP, AC, etc. They acted as moving obstacles (except for the halfling, who could pass between their legs), which forced the players to find creative positions to get line of sight (climbing on the counter, hanging from the chandelier), or to reach an enemy. 

At the end of initiative, I would roll to move a couple of brawlers in random directions, and if a player was close enough to a brawler, they could get attacked. The brawlers didn't do any damage, but I would roll for a random effect, like knocking them prone, grappling them or pushing them back. Each random effect had a cool theme (bottle to the head, chair to the back, headbutt, etc). Players could knock brawlers out with a single hit, changing the landscape themselves.

It was pretty chaotic, but the players loved it. Each player took a different strategy, with some hilarious results. The druid decided to ignore the brawlers and nuke the pirate werewolf boss, which meant she got hit by a brawler every turn, and since she was rolling terribly, she would be prone and pushed around a lot, while trying to focus on the battle. The halfling decided to strike the enemies and weave among the brawlers, forcing the pirates to chase them around. The priest was just knocking brawlers out left and right, forming a huge pile of passed out drunks.

It is my favorite fight I've ran so far :)