This one was a bit hard, because I'm generally willing to go along with canon and take it as is, even if I don't like some of it.
1. That stupid godawful thing about House being abused as a kid. I totally have a huge aversion to "omg abused as children!" as any sort of character background, mostly because it's almost always used as a shortcut to angst or something and therefore always triggers "DANGER: BAD CHARACTERIZATION AHEAD" signals in my mind. Also, I feel like it almost simplifies House's relationship with his father a lot. I'd much rather have them work to construct why House and his father don't understand each other, rather than just saying "Well, it's just because House was abused as a kid." Because to me, that's a really unsatisfying answer.
2. All of Black Market. Seriously. WTF?
3. Can I count the FMA movie as an episode? I hated it a lot. Or at the very least, disliked it tremendously. Mostly because a lot of the plot points weren't really built very well, and there was so much Deus Ex Machina-ing all over the place. Also? Hughes as a jackass Nazi, which wouldn't be so bad if they built his story in any meaningful way, gave some sort of reasoning behind it. Maybe I'll watch the stupid movie again and try to write the story of how alter!Hughes became a Nazi, just so that I can justify it to myself. BTW, why the fuck is Roy punishing himself again? I keep on feeling like there was a reason. Oh, right. I KEEP FORGETTING BECAUSE IT WAS FLIMSY.
4. Maybe David Brent doing the awkward dance in The Office (UK). Not because it was bad, but because whenever I see it, it hits my embarrassment squick and I kind of want to curl up and die.
5. The podrace in TPM. Okay, so there's a lot wrong with the prequels, in terms of dialogue/scenes/whatever, but nothing pissed me off more than the podrace when I watched TPM, because holy shit, it's such a waste of time. It's just sort of there.