I hate the name Hannah, Jessica, or Madie. I know at least four Jessicas in real life and even though they all have different personalities. I always end up cringing while reading a story where I can see the person in real life doing it.
I don't like the name 'Harry', either. I always end up thinking of Harry Potter and it makes me think "...Harry wouldn't do that." Then I have to remind myself I'm not reading an HP story :3
On another note, I read a lot of One Direction fanfiction as well, and that's about the only time I don't think of HP
Other random names I cringe at: Caleb, Nick, Courtney, Denise, Ron, Cassidy, Michelle and Benedict / Benjamin.