There's quite a few on the list...
I voted for bears and zombies. I would also like to add DEER. So many guns are compared to how well they kill a deer, on this and on other forums. I know lots of people deer hunt, but seriously?
Both the deer and the zombie threads strike me as a more "polite" way of asking "What gun is best for using on people?"
Another thing is the hunting ethics stuff, as another poster mentioned. If I hunt, it means I'm HUNGRY. Shoot to kill, kill to eat. I'm not really interested in what is "sporting" or not.
As for the bears, I have two uncles who live in areas where there are bears. Lots of bears. Neither of them has seen one except at a several hundred yard distance, and as much as I've been to where my uncles live, I've never seen one at all. Reading the bear threads, you'd think these things pop up in your yard like toadstools.
The "taking our guns away" threads are irritating, but I find them so because the information contained in them is generally not accurate and is also out of date. There's plenty of things to worry about concerning our rights, but these threads typically miss the mark.