-"Autistic" referring to someone you disagree with, in particular in YouTube comments.
-"Cis", in regards to gender. I realize there has to be an opposite of "Trans", but I just don't like the word. It makes me think of molecular structure and not humans.
-"Lad", especially from a teen/young adult when referring to oneself or ones friends. It almost always indicates some kind of macho behavior and makes me want to not know them.
-"Cheers" as in "thanks". It feels dishonest, and since I moved here to the UK it keeps popping up.
-"MRA"/"SJW", both tags that have been made up to avoid meaningful debate and just label anyone who disagrees with you as bad.
-"Neckbeard" We've gone back to judging peoples personality by how they look? Really?
-"(Wo)man hating" Just because someone isn't as invested in equality as you, doesn't mean they hate women. Just because someone points out men have privileges doesn't mean they hate men.
-"White Cis Male" It's a way of shaming people, just those people who tend to be more privileged. "You were born into a segment of population that makes it more likely you'll lead a good life and you should feel bad!". It's not like every white cis male is Rockefeller, either, there's plenty of white, cis, male homeless people.
-Saying "no one really cares about X". No, sorry, someone cares, or you wouldn't be discussing it. I understand it isn't meant to be literal but it ticks me off.
-"Weeaboo" Most people who use this are nerds. Why do we have to invent a term to shame a particular kind of nerd? It's not like we don't get enough of that already.
-"420". I just still don't understand why, and it always takes me a few seconds to remember.
-Any phrase that's over 30% hashtags or the words "YOLO" or "swag", unless it's being used as a joke.
-Saying you "like something ironically". It feels like you're trying to be to cool for school.
-"I've got a theory..."/"But that's just a theory!". No. A theory is the highest level of scientific truth. Your guess about a random thing isn't a theory, and saying "That's just a theory" is equivalent to "That's only been proven to be true as much as it possibly can be"
And, the one that makes browsing the internet a nightmare...
"LOL". There's something about it that just drives me fucking nuts. I can't stand it. It hurts me. It hurts me so bad. Funnily enough, I don't mind it in spoken conversation, but on the internet it just makes me very, very upset, and is EVERYWHERE.