Sports - I don't like competition sport (probably because I'm bad), I especially hate watching sports. I can't even begin to understand what's fun about watching someone else do sports (especially professionals, who are infinitely better than you are). You aren't creative, there is no story to follow, you're just wasting your time!
Pets - no real problems with pets in itself. I wouldn't keep them myself as I'm allergic. But I don't understand people who are totally emotional or connected to their pets or any animal that's pet-worthy. Yes, I know that my rabbit stew comes from cute bunnies. No, don't expect me to gush about your little dog and please don't act hurt when I won't touch it because of my allergies, as if my love for that animal shouldn't be damped by trifling practical problems.
I don't understand people who aren't interested in science. I'm not talking about the physics lessons at school or the like. They are full of formulas and abstract models and you've got every right to not liking those.
I'm talking about the sort of science on the level that you (general you - the level adapted to the person) can understand. I'm talking about the person who doesn't want to know how a rainbow is made and is disappointed when told, because "knowing destroys wonder/magic/...". I don't understand this.