Street Fighter 4 when the AI resorts to cheating, mainly on the higher levels. There's a difference between making an AI more skilled and just letting it ignore the rules of the game. Guile pulls off a sonic boom with no charge time, Blanka and his damn roll, etc. It makes me absolutely furious. Example, I'm playing as Ken and the opponent is whoever. Opponent attacks and at the perfect moment I let rip with Ken's special (whatever it's called, that vertical dragon punch). Suddenly, the opponent who was until a microsecond ago totally open now blocks the attack and, nine times out of ten, comes back with their own super...which, of course, never misses and is nearly always timed to start one frame after yours, which means it will take priority over yours. This happening once could be considered lucky, but it happens again and again. It is flat-out cheating.
I've even had attacks blocked by AI characters whose backs were to me when I started the attack. That's pretty impressive.
Besides SF, hmm...my main beef is with games which are not programmed well enough to allow the player to do what they're supposed to, maybe because the controller reacts way too slowly. You know what you have to do and you do it, but the response is too late and consequently you get killed. That's a good controller-throwing moment too.
I have this theory which I call "the 3 time boss rule". If a boss in a game takes more than three attempts to beat, then it's badly programmed. The first time it can beat you because you don't know the pattern, the second time it beats you because you know the pattern but haven't worked out a way to counter it, the third time it wins because you know the strategy to win but can't carry it out. Once you've worked that out, the only way a boss can beat you is if you make a mistake (which is fair enough) or the boss blatantly cheats (which is not fair enough).
