I'll tell ya the most annoying moment in FFX. The most annoying moment in FFX is when the freakin' Prologue didn't play like it usually does. That seriously agitated me. (Would that even be a moment? It didn't even happen...sheesh. I guess it counts as a moment seeing as I was waiting for it to play during the ending theme.)
Other than that, the final boss guy who kept making me go through that icicle/item area thingee and watching the whole transformation scene over and over and over again after killing me countless times.