Boss Fights: Tedious, boring, game stoppers that reminds me that I am playing a video game (insert sound from Galaga or Invaders here).
Respawning enemies: Especially in completely impossible locations. I just cleared out room A, which has impenetrable concreate floor, roof and walls, just to be stabbed in the back by critters appearing out of thin air the moment I turn my back on it. It doesn't give the impression of vast numbers, it gives the impression of bad design/shortcuts
Forced companions: 'Nuff said.
Unkillable npcs: Just as bad as indestructable environment and 1 foot obstacles that you can't jump over. I don't care if it turns the entire world hostile and prevents me from completing the game. Powerword Reload is the lesser of two evils (immersion breakers).
Save points: Somebody once tried to convince me that it wasn't a limitation of the very first game consoles and their flash memory sizes. They didn't succeed.
The idea that first person perspective somehow equals immersion: No, artificial tunnelvision and lack of peripheral vision does not equal immersion.
The constant need for "streamlining" (politically correct term for dumbing down?): Ok, so the mainstream population might have a short attentionspan. Games designed for those who doesn't have that seems few and far between. Yeah, I know, it's all economics. Rogue Trader *was* more fun than the current GW drivel that they pass off as WH40K
Romances: Muahaahaa!... (see "streamlining", alternatively "shallow"). Nice dress, let's have sex.
Hybrid games: Action is fun, roleplaying is fun, adventuring is fun... lets do everything and achieve none of the above
...
Insert long continous rant here