-Unrealistically big-breasted women with armour that doesn't look like it can protect a fly.
-The above co-existing with male troops who cover up as much of their bodies as humanly possible. (Guild Wars, I'm looking at you.)
-"Realistic" colouring schemes....meaning shades of gray and brown. When will people designing realism realize that not everyone else is colourblind and there's some actual colour?
-World War 2, Sci-Fi-Powersuits, Ye Olde British Isles, and Feudal japan settings that we've seen enough times to constitute a use of the Vegeta Meme.
EDIT: How PC Games assume you have a system restore point without taking into consideration that there are a lot of people out there who don't know how to do that or your dumbass family member who knows even less than you do manages to completely fuck up the computer beyond recognition, or that Viruses that wipe out your hard drive don't exist, meaning you got a copy of Bioshock that's little more than a coaster since you can't enter the bullsh*t serial code and can't even upgrade your computer.
-PIRACY.
-The "let's be like Half Life/Halo/Doom" mentality that have been making FPS Games sh*t for the past few years. If I wanted to play Doom, I'll just download Doom and play that.
-Western RPGs that try to make the interface about as complicated as possible. (See: The Witcher) If that's supposed to be a sign of intelligence, then I'd rather be dumb as the average Counter-Strike/TF2 player and having fun than playing a game that'd put Stephen Hawking to sleep.
-JRPGs that send oyu on wild goose chases.
-The "You gain HP by losing HP, you gain MP by casting spells, you gain strength by attacking" leveling up system. Can you like, not do that guys? That frustrated the hell out of us in Final Fantasy 2 when clubbing ourself over the head gave you better experience. It only really worked in Morrowind or Brave Fencer Musashi.
-Elitist "PC games are better than you all! Consoles are for stupid people and they suck!" gamers. Remember when the point of a game was to have FUN?