(Strictly for fun: a compendium of the most illogical rules oddities in 3.5. Posted here because nobody else is going to have the same command of rules arcana.)
YOU MIGHT BE PLAYING 3.5 IF...
1. A level 20 Gnomish Expert with 23 ranks of Alchemy, 23 ranks of Knowledge (Alchemy,) and Skill Focus: Alchemy is utterly incapable of brewing a flask of acid.