Ultima Online/YMMV


 * Demonic Spiders - Seriously, is there a magical enemy that doesn't follow the poison-paralyze-flamestrike pattern ?
 * Game Breaker - Many over the years, magic, plate mages, crossbows, animal taming, bards, and of course "Vas Corp Por".
 * Germans Love David Hasselhoff - The game is bigger in South Korea than it is in the US.
 * Goddamned Bats - Sewer rats and slimes. They're everywhere. They pose no threat to anybody, but they tend to interrupt healing and spellcasting with their nips.
 * They Changed It, Now It Sucks - Very nearly everything they've ever changed. Trammel, the notoriety system, labeling potions so you can't give newbies purple ones to watch 'em blow up. Stopping potions from chain-exploding et cetera.