Alignments and by extension the Paladin's Code of Conduct, order of rules, FAQ isn't rules, Errata is a flawless holy grail, Dragonwought Kobold, Psionics is OP, TOB is too anime and Fighters can't have nice things, Bards & Monks suck or alternatively Monks & Barbarians are OP, the rules don't say I'm wrong and RAW means everything is quoted out of context and defined by my intent ignoring any other opposing rules. Lots of class vs class, notably Fighter vs Wizard which led to JK's Factotum rebuttal. Oh and you can't forget stuff like the Lightning Warrior.