Favourite game is Mass Effect 1, but I don't think I have a pet peeve because a lot of them have been said before (love the Mako though, it's just that the planets BioWare built are all fucking hills!)

But I think my pet peeve for Mass Effects 2 are 2 things.

1. The fact that there aren't scars in 2. Unless you use mods, but I like having my Shep's look battle-worn.
2. That BioWare made Shepard work with Cerberus. Like I get it in the idea of "the Alliance isn't saving people, but Cerberus did". But it feels so wrong especially if you played Mass Effects 1 where you can see the experiments Cerberus did on civilians. That and if you have the Sole Survivor background, it's a real slap in the face.

I know that they did 2 for storyline purposes, but the fact that you can't push back or anything makes 0 sense. And they also did it for people who never played 1. I just, ugh. It angers me. I love that 2 gave me my Garrus romance, but man, I just... yeah.