Tidus, from Final Fantasy X. No other character has annoyed/pissed me off so much as him. I actually quit playing what was otherwise a fun and enjoyable game because he dragged it so far down. He's such an idiot, so annoying, he never once acts like a real human being? just? gyah. And, um, stabbing him with the Brotherhood sword. Repeatedly. In the gut. Either that, or I'd call up Ezio, hand him the Brotherhood sword, and ask him what sort of inventive finisher techniques he could come up with for it. I'm sure that impractical fish hook could do something nasty.