This is just my own little hang-up, but I have a really hard time seeing any sort of animal cruelty rendered on-screen (though I strangely have no problem watching people be killed*). It pulls me out of the movie and upsets me enough that I usually end up either being unfairly harsh towards the movie or just turning it off.
For whatever reason, I seem to be on a really hot streak as far as picking just this sort of movie lately. First was Terrence Malick's Badlands. The most recent, and much more egregious offender, is Tarkovsky's Andrei Rublev. I only made it about 2 hours before I was so upset that I had to turn it off. Every time something happened, I kept trying to reassure myself that what I'd just seen wasn't real, that there was some way to fake it, but a couple of the instances seemed real. I just don't see any reason for that sort of stuff to happen on-camera. If such story points are really so important to the film (and I can't really think of a reason why they are), at least do it like the dog's death in Jaws where it happens completely off-camera.
Yes, I'm a spaz, and I realize it. This hang-up probably subtracts from my enjoyment of some really great art, but I can't help it. Does anyone else have something that similarly impedes their enjoyment of films/books/whatever?
/blog
* - In movies. Obviously. What kind of monster do you think I am?