humm, one of my most hated moments involved Black and White. Near the last zone, there is a quest where you need to retrieve a potion before a town gets too sick and dies. If you succeed, you get to make your pet a wolf. If you fail, you don't. Well, due to a certain bug, failure was the only option
Needless to say, I replayed that mission to the point where I single handedly razed the entire town and surrounding area to the ground, by 'hand', until I exhausted all possible options and realized that the quest was in fact a bonifide bug. Remember never to put a banevolent diety into a broken, nested loop, they'll go barmy and destroy your world
Come to think about it, I haven't played B&W since that day, nearly 3 weeks after its release. Don't get me started on trying to backup a profile . . . *wonders if a pressed CD will react differently from a burned CD in the microwave.*