My biggest pet peeve would have to be people that are assholes for no reason.
(I'm not talking about anyone on here, if that's what it sounds like. I mean people I have to deal with in real life when I'm going to class and stuff like that.)
Other than obvious ones like being picked on or watching people torment defenseless stuff like children, animals, plants and inanimate objects-- I really despise people who talk badly about robots or other AI type things, characters of fiction or real. The heavy labor/assembly robots in several factories already attack people to the point that they have to have fences up to stop them from coming in contact (kid you not) or turn them off to inspect them. We hardly understand why we have consciousness, I don't know why we're so arrogant as to believe that we could recognize it in something else. What if whatever it is just doesn't think reacting to our questions or tests is important?
Desert Rosy Boa, pretty much the best snake you can get. They're cute, non-aggressive, easy to care for, and stay small. And they are native to California, which makes them even cooler (I'm really interested in native Californian herpetofauna).
How I get a "rushing" kind of noise in my ears when I'm in a class and the teacher's talking and every time he/she pauses for a moment.....*shudder* that rush. I've always had it a little I think, but I made it a lot worse when I went to that Marilyn Manson concert and left my earplugs in the car.
The textures of flat-painted drywall, certain kinds of non-glossy paper (I'm obligated to scratch them with my fingernails just to see if it still irritates me and just thinking about it is making me edgy), and ultra-suede and any other fabric that "catches" on my skin when I run my hand over it.
Slimey okra. If it's not slimey, it's great. But otherwise it's like eating gigantic fried boogers.
Scene kids. Maybe not intentionally annoying, but they do a great job of it anyway. Also their music and everything about their scene personalities, including their rampant acceptance of homosexuality which I think would otherwise be great, but just about every scene kid I know considers himself or herself "bi" and honestly, it's only because it's cool to be that way.
The little noises that everyone in my lecture hall makes that I can hear when the professor stops talking... Paper crumpling, coughing, sneezing, whispering, giggling, backpack zipppers, pages turning, foot tapping, etc. And with 500 students in the lecture hall, it becomes quite unbearable; I've actually had to leave my classes early because I couldn't take hearing all that noise.
Spelling, grammar, and usage errors in contexts other than casual conversation.
Electronic noises.
The inability to edit and correct spelling, grammar, and usage errors in contexts other than casual conversation especially when surrounded by people who point it out and/or are bugged by it.
pet peeves--
--people saying "girlfriend" when they mean "friend"
--half the things my little sister does, like--
--eating all the food in the fridge (and all the ice cream in the freezer) and then complaining that she wants to lose weight and can't, and
--when she uses my hairbrush and gets all her long curly red hair in it, then I have to pick it out before I use it, and
--when she's a slob, and
--when she nags at me
--air conditioners
--fluorescent lights
--the smell of cheese
--people telling me to stop tapping my foot and shaking my leg
--those commercials on TV that tell you all the reasons why smoking pot is bad (those commercials are rude and offensive to pot-smokers, and it's uncalled for)
--those commercials telling you that cigarettes are bad for you. stop making commercials about cigarettes being bad for you. everybody already KNOWS that, so get over it. we don't need to hear it over & over again.
I hate it when I'm eating Frosted Mini Wheats, and then I get one with no frosting. If I wanted to be eating flavorless shredded wheat cereal, then I'd eat some dry Weetabix instead.
Doctor's/Dentists offices and the never ending circular paradigm of phone tag trying to make appointments, schedule with specialists, get the referral in the right number of hours figuring out where the specialist is, when is a good time so the kids don't have to be taken out of school, finding a sitter when needed.
ARGH! It's so stressful, when it's not for my kids, I won't do it. Which is why I only go to the doctor for myself when I'm so ill my husband schedules it.
Had to get that out - now to try calling AGAIN...
the annoying music while on hold at the doctor's office....

Drivers who think they're entitled. I may have said it already, but it gets worse every day.
The funny part is, they weave through traffic to get ahead of everyone else and I still end up right there with them anyway.
Also, people who try to argue against evolution but have no **** clue what they're talking about. Stuff like "well, I know MY grandpa wasn't a gorilla" and "*I* was never a tadpole!"
...honestly.
I'd say something to litterers but I'm afraid they're the kind of people who are more likely to shoot me.

-Car salesmen type of people. (Say a guidance counselor trying to get you to enroll in their school within minutes of getting the first call form them EVER about the school--stop trying to rush me!)
-People who follow something blindly and without question.
-My Mom's dog will eat cat poop if she can get to the litterbox unnoticed. (So disgusting!)
Some dogs have been known to eat human poo. I don't know how they can do it.
Nyanchan, that case with the kittens was in my home city. The guys were in the army and got booted out. Apparently, they were all drunk and one of them was the ringleader and the others stupidly followed him. Sadly, some people have no respect for animals or humans for that matter.