The CU (Publish 15)
Because Star Wars Galaxies was so unpolished when it launched, many elements - even major game elements - were partially implemented or poorly tested. The BioEngineer class, for example, was added just a week or two before the title hit store shelves. As a result the cloning expert in the game was a barely functional mess. The main combat system was fully implemented but, despite the lengthy Beta test, was also highly idiosyncratic. In an effort to answer player concerns and streamline the game's playability, the designers undertook a massive overhaul of the combat system. Where, previously, every character was allowed to use every item (more or less) there would now be restrictions on who could use what. There would be clearly marked bonuses and penalties for using certain times of armor and weapons, and how weapons and combat worked would be clarified as well.
It was easily one of the largest changeovers attempted in a post-launch MMO, and the hope was that clarified combat would attract new players. The current players were vocally opposed to a number of elements in the CU, with entertainers and crafters the most vehement. Those classes - once able to sally forth into combat alongside their big-game hunting friends - would now be restricted to pea-shooters and cardboard robes. The catch - the thing that few people recall these years later - is that the Combat Update worked. Afterward players found engaging in combat a far more rewarding experience, and (the rumour goes) subscriptions actually rose back to at-launch levels. Perhaps even beyond.